The day of my daughter's fourth birthday party, July 14, 2002, started out sticky hot. By 9 a.m., Sophie had skinned her knee running favors from our car to the picnic tables at our swim club. Inflatable beach balls, leis, bags of gummy fish -- the whole tropical gamut -- had spilled out of our cardboard boxes, and my daughter, bathing suit clammy under her shorts, was sobbing. Meanwhile, I was fuming.

My mother and younger sister, Candy, 42, were supposed to be there, helping me and my husband get ready. They and Candy's boyfriend had driven up from New Jersey to join us in Brookline, Mass., two days before, and had promised to watch Sophie that morning while I set up. But with the party looming, they were nowhere in sight.

I bent down and gathered Sophie in my arms. Where were they? It was just like Candy: Offering to "wash the dishes" or "give Sophie breakfast" or lend a hand in some way, but then messing up to the point where I had to do the job myself. She hadn't always been like that -- just a couple years ago, when she'd been practicing law out on the West Coast, she'd been so dedicated and responsible that the family had jokingly referred to her as "The Good Woman of Oregon." But in the fall of 2001, she had moved east to help out our mother and had grown increasingly self-absorbed and scattered.

By now, I told myself, I should have expected the lateness. In fact, Candy had been late everywhere all weekend, and not by just a few minutes. On Saturday, she'd taken my mother's car to follow me to a kids' ceramics workshop, then somehow veered off in an unknown direction and not shown up for two hours. She said she'd gotten lost. When I'd remarked to my mother later that Candy had a really bizarre sense of direction, she lit into me for being "judgmental."

"Well," I'd said sternly. "Some things should be judged."

The day of the party, by the time my mother's green Volvo finally swung around the rotary, half an hour late, I was feeling even less charitable. But when my family got out, sunshiny and oblivious, my anger morphed into astonishment. Candy stepped into our suburban landscape of blue skies, chlorinated pools and brightly colored balloons wearing the outfit of a hard-lived weekend night: ratty black jeans; a threadbare camisole and a long-sleeved voile blouse in dingy white.

"You look like you're going to a nightclub," I said, stifling a laugh. In fact, with her gaunt face and torn, dirty nails -- two other developments of the previous year -- she looked like she might be coming back from a three-day rager.

"It's the closest thing I had to a bathing suit," she replied skittishly, before wandering off to smoke a Camel.

I let my alarm pass -- as I had many times that weekend -- and began to spread out the fish-themed tablecloths. Then, for the next two hours, Candy disappeared again. Once or twice I wondered where she'd gone, but mostly I was laser-focused on the party -- herding 12 preschoolers from the pool to the chicken wings, parceling out the overflowing goody bags. Candy showed up again when nearly everyone had left, running back to us across the field, so skinny her bones seemed to rattle.

Looking back, if I'd taken the time to see beyond my life into hers, Candy's choice of "swimwear" should have been the last in a long line of increasingly shrill warning bells. There were the false teeth she'd had to get because of "a rare gum disease" (my mother told me her mother had had gum issues, too). The frequent naps -- in a chair, in the car, on my rug. The strange secondhand gifts -- pieces of used teleconferencing software for me; boxed beige tap shoes for Sophie. The way she'd fought me -- bitterly, unrelentingly -- when I'd refused to let her take my bike out late one night. And perhaps most telling, my own physical reaction: The girl I couldn't keep from crushing into a hug well into her teens had become a woman I didn't want to touch.

I wouldn't learn for two more months -- until, in fact, after her arrest in New Jersey -- that there was a reason for my sister's odd get-up and strange behavior. She'd become addicted to methamphetamine, a powerful synthetic stimulant once derided as "the poor man's cocaine." The drug is easily and cheaply made from ingredients found in most drugstores and hardware stores. When snorted, smoked, eaten or injected, it grants a long-lasting high that floods users with a powerful sense of alertness and well-being. It also starts destroying their bodies and brains. The long-sleeve shirt and pants that I saw at Sophie's party were to cover the tracks and bruises caused by shooting home-brewed meth. And the lateness I witnessed wasn't merely a personality quirk. Candy and the boyfriend had been busy cooking up batches of the toxic drug in their hotel room and, driven by the compulsive collecting behavior that's often one of its hallmarks, diving into dumpsters for "treasures" on their way to the ceramics shop or the mall.

According to the U.S. government's 2004 National Survey on Drug Use and Health, 11.7 million Americans have used meth illicitly in their lifetime, including nonmedical use of its prescription form. A full 1.4 million have used it in the past year. Users, most of whom are white and more than 40 percent of whom are female, run the socioeconomic spectrum: poor, rural teenagers on a binge; gay clubbers; suburban mothers trying to "do it all." Writing this today, I'm amazed I didn't pick up on what was happening with Candy, but, back in 2002, meth was still working its way from the West Coast across the country. My family got to learn about the drug firsthand, before it really started making local headlines.

Candy, 7 1/2 years younger than I, had always been my baby -- a little girl with golden curls that I'd sweep up from her ears into a cascade on top of her head. I was her safe haven, and she was mine. As adults we shared another bond. Before Candy got lost in meth, we were the ones who would talk in depth about our crazy childhoods, sharing insights in an attempt to make sense of our adult fears and longings.

There was a lot to discuss. Our father, at once dashing and tyrannical, was a mechanical engineer turned stock market gambler who spent a good part of his adulthood steadily sliding toward a psychological crash. Each year he got more furious, more impulsive. Candy -- the youngest of four -- missed the better days. By the time she was four, our father was paranoid and prone to physical rages, smashing furniture as my mother fled outside to sleep in her car. Candy, sucking on two fingers of her right hand, was often the one to let her back in come morning.

Our mother finally committed our father to a mental hospital in 1964, after he'd stood in the driveway copying down the license plate numbers of the "spies" who were after him. He died in an accidental fire roughly a year later, long after he'd been released from the hospital, at age 40.

Growing up, I responded to the confluence of madness and silence in our house by being the "perfect" child, the super-responsible one who always got straight A's. Candy took a different turn. She'd been sexually abused by some neighborhood teenagers and by an instructor at a ski resort, though I didn't know that at the time. By her teen years, after our mother remarried, Candy had started to drink, smoke pot and occasionally snort cocaine. Later, at college, her experimenting went deeper and darker: Dilaudid (a morphine derivative), even heroin.

At the root, she says, was a feeling of deep inadequacy and guilt. "Drinking and drugs made me feel like I could interact with all those people who were smarter than me," she says now. "As if what I thought mattered -- as if I mattered."

I was frustrated -- even angered -- by her, but in the back of my mind I worried that she'd "caught" whatever had ailed our father.

Still, there was one area in which I could be wholeheartedly proud of her: Candy never let go of her desire to be a lawyer. Specifically, she wanted to be a juvenile-defense lawyer, to help kids coming from troubled families like ours. So no matter how messed up she got, she always managed to shake herself clean in time to maintain the grades she needed to achieve that goal. She applied to Willamette University College of Law, in Salem, Ore., and was accepted to its Class of 1986. Once there, she also finally got sober, figuring that she wouldn't be much help as a lawyer if she was drunk or scrounging for drugs.

Candy would be clean for 15 years. Then in 1998, she started slipping. Unfortunately, meth caught her.

Methamphetamine, an extremely potent form of the stimulant amphetamine, was first synthesized in Japan in 1919. Decades later, during World War II, soldiers and pilots on both sides were given doses to combat fatigue. The drug was available in various forms for many years after. But in 1970, it was classified as a Schedule II drug, illegal to possess without a prescription, and it went underground.

Then, in the 1980s, when new, easy-to-follow recipes for meth began to circulate, its clandestine manufacture picked up in the West. Mexican cartels also discovered a lucrative market in cooking up the drug and exporting it north. Over the next 15 years, meth's use exploded in Southern California and spread from there. By the mid-'90s, Eugene, Ore. -- where Candy had hung out her shingle as a juvenile-defense attorney -- was flooded with the stuff.

Read more about the history of methamphetamine.

In her years there, Candy had made a name for herself winning case after case that other lawyers considered lost causes. She was a pit bull when it came to protecting kids, whether that meant returning children taken by the state or finding them new temporary homes. But battling the state office for children was draining and often demoralizing. That year, the son of a client died after overdosing on an antidepressant in foster care, and another child was placed with his dad, an abuser, despite Candy's entreaties that he be sent to live with his mother.

"I kept taking on more and more cases, and feeling like I had to win the type everyone considered unwinnable, until I was completely overwhelmed," she says. "Even when I did win them, I'd feel just adequate for maybe five minutes."

To dampen her feelings of helplessness, she started drinking again. Pretty soon it was every day -- rotgut wine in boxes. But I didn't know that. As far as I knew, she was still trying to save the world.

In the winter of 2000, Candy decided she needed to take a breather. She'd close up her practice for a month and maybe come east to help our mother care for our stepfather, who'd just had his leg amputated as a result of complications from dialysis. I urged her to do it. With a toddler at home and a full-time job in Boston, I thought it would be ridiculous for me to go myself, but our mother did need the help. "It will be a good thing for all of us," I told her over the phone, comfortable knowing she would assume the burden.

Before packing up, though, Candy decided to take meth, both as a form of escape and for a little extra boost in finishing everything she needed to get done. She didn't expect any trouble: She'd tried the drug before, when a roommate gave her some, and hadn't particularly liked it. In comparison with cocaine -- a stimulant she most definitely had a taste for -- meth seemed safe.

"I just wanted to get high," she says.

"I figured I could do it for a week and then quit."

Candy began by drinking what's known as "biker's coffee," a brew of the white powder and java that's been popular among affluent urban users on the West Coast. Meth's effect has been described as a burst of pure nirvana: In a Rolling Stone interview, meth addiction expert Alex Stalcup, director of the New Leaf Treatment Center, in Lafayette, Calif., likened it to "the chemical equivalent of 10 orgasms at once." But for Candy "it came on slow," she says. She got just a little rush -- kind of like wind in her sails -- but it was accompanied by a powerful sense of concentration that blotted out any feelings of inadequacy. She could spend all night pounding at the same two nails -- again and again -- and think she was a success at building shelves.

She never did really get to love the drug; instead, she says, "I just got addicted to it." From the beginning, she used several times a day. After a couple of months, she advanced to shooting it -- having seen too many toothless meth addicts, she was concerned that eating the drug would rot her teeth. (It eventually did anyway; "meth mouth" results from the dry mouth, tooth-grinding, poor dental hygiene and penchant for sugary foods common among users, not from contact with the drug.)

Feeling she had a reputation to protect, even as the drug gripped her tighter, Candy carried old legal files whenever she scored. "I didn't want to run into clients and ruin my law career," she says. She figured that if colleagues -- or the police -- saw her, she could claim that she was working as an attorney for the dealers. It was on one of these jaunts that she met her boyfriend, an ex-plane mechanic who lived in a trailer home in a Eugene parking lot and dealt meth. Contrary to the drug's reputation as an aphrodisiac, Candy says sex on meth wasn't great -- or frequent. "Sex interfered with my drug use," she says.

About three months after her first hit, she was evicted from her apartment for nonpayment of rent -- a fellow addict, invited in to use, had stolen her rent money. She moved into her basement office, but lost that, too, within a matter of months, after the landlord barged in and saw the floor strewn with the detritus of a shooting gallery. Now officially homeless, she moved into the boyfriend's trailer.

"Initially, I was really careful not to be seen because I didn't want my reputation to be harmed," she says. "But I rapidly became oblivious."

That was partly because she'd discovered her first "tweak" -- the thing a meth addict has to do over and over again. When she was high, which was almost always, she had to be on the computer -- diddling with programs to make them run faster, ordering freebies on the Internet. Then computers faded, and she was obsessed with diving into dumpsters -- rescuing audio equipment from behind Radio Shack, pens from behind Office Depot.

Compulsion is a part of all drug addiction. A 2001 study led by Nora D. Volkow, now director of the National Institute on Drug Abuse, showed that cocaine, heroin, meth and alcohol abuse all affect the chemical processes in the orbital frontal cortex -- the same region of the brain hampered in people suffering from obsessive compulsive disorder. Meth seems to have a particularly strong effect. It creates something like an uncontrollable itch. The abuser has to scratch -- and scratch and scratch and scratch.

"Meth addicts' minds are racing, overstimulated -- they get tremendous reward by doing the same thing over and over," explains Stalcup. "I've watched people take apart clocks and sewing machines by the hour . . . They can't stop. If they pull out of it, they feel negative in a minute."

Finally, in September 2001, 10 months after she'd originally planned, Candy arrived in New Jersey. She resumed her dumpster diving that first night. At 10 p.m., while my mother and stepfather were watching "Law & Order," Candy hopped on her bike and whipped through the streets, past the huge colonial houses with SUVs in their driveways, to the dumpsters in the center of town. She balanced her finds -- a suitcase, a broken bicycle -- on her handlebars, and came home to stash them in the finished basement of the suburban ranch house where we'd grown up.

Finding meth, though, wasn't so easy for her. At the time crystal -- a pure, crystalline form of the stuff -- had become popular in Manhattan's gay clubs, but meth hadn't (and, in fact, still hasn't) migrated to the urban Northeast in a big way. As far as Candy knew, it hadn't come east at all. So when the boyfriend joined her a month later, arriving by bus, they used a recipe found on the Internet to begin making their own supply, first on a hot plate in the basement and later in Candy's old room, beside her white Ethan Allen desk set.

While the Drug Enforcement Administration estimates that 65 percent of the meth sold in the United States is now manufactured in Mexican "superlabs," most of the remainder is whipped up north of the border. Unlike cocaine and heroin, meth can be made by anyone holding a recipe, in everyday kitchens, hotel rooms, public storage lockers -- even car trunks. The whole process can take less than four hours -- with, experts say, five pounds of hazardous waste created for every pound of the drug. Dana Hunt, the principal scientist behind a recently released monograph on meth use put out by the National Institute of Justice, says that, in many cases, "you're not dealing with some exotic drug dealer; this is the neighbor's son."

Or my sister.

In between driving our stepfather to his appointments at the synagogue, the auto school or the barber, Candy and the boyfriend would scramble to collect the common household chemicals they needed to transform pseudoephedrine -- the drug's prime precursor chemical found in many over-the-counter decongestants -- into methamphetamine. At the local supermarket, Candy swept Sudafed packets into her backpack by the handful. For red phosphorus, another necessity, she spent hours scraping the strikers off matches after, say, dropping my mother off at her exercise class.

Candy and the boyfriend made only small amounts of the drug at a time, which may explain why no one in the house noticed any noxious fumes. "You didn't smell it, when you visited that fall," she tells me now. "We were making it in the basement. I kept running downstairs, asking, 'Is it done yet? Is it done yet?' and then racing back up to see you."

Cooking became the boyfriend's tweak: He even did it while we were sitting shiva after our stepfather died in November 2001.

At first, having Candy and the boyfriend staying with our mother had meant I could comfortably be more than 200 miles away, living my life. But a few months after our stepfather's death, I began to think of them -- and especially the boyfriend -- as freeloaders. I'd call up Candy and insist that she take a job, any job. When the boyfriend answered the phone, I'd lecture him, saying he was poaching off an elderly woman. But as long as our mother continued to support them, nothing changed.

Burglary became Candy's tweak almost accidentally that December, during a family vacation at a mountain resort -- a place with hearty breakfasts and a toboggan run. Candy and the boyfriend were desperate to find the iodine needed to make a batch of meth. When they spotted a horse barn on the property, they imagined a veterinary first-aid kit inside and broke in. There was no iodine.

But they did find a computer that they brought back to their room.

Candy would only break in to empty buildings -- homes under construction or abandoned; detached garages; public storage lockers -- because that meant, to her juiced mind, that the things she took didn't actually belong to anyone. Getting into the properties was easy so long as the windows had wooden frames. Down to 94 pounds from 115, she'd pop the pane, flip the lock and clamber into the darkened space, paint chips from the sill rising behind her like smoke. Once she discovered that the storage lockers she'd rented for her overflow had open tops, she began scrambling, spiderlike, from unit to unit.

For nine months, the filched property piled up in our mother's garage, on the woodsy hill behind the house and in the attic. As far as I could see, our mother never questioned the clutter, cheerfully telling me, "Candy's been going to yard sales." But Candy tells me now that they had screaming fights about the jammed garage, which is why she rented a storage locker in the first place.

Candy was apparently an indiscriminate thief. She had stacks of power tools, boxes of jewelry (real and costume), collectible figurines, comic books and high-end computer equipment. There were size 14 dresses, stuffed animals, kids' watercolors and garbage bags full of people's identification: driver's licenses, credit cards, checkbooks. She never used any of it. She organized it. For hours on end, she'd shift pieces around in big, gray plastic containers. She'd even return what she didn't "need."

After Candy was arrested in the fall of 2002, a local newspaper would report that, all in all, she had raided some 18 homes or garages and nearly 20 storage lockers -- upwards of $35,000 in stolen goods from three towns in two counties.

On the morning of Sep. 20, 2002, Candy was returning home after another scavenging expedition when she saw a police car in our mother's driveway, parked alongside our stepfather's old Grand Marquis. Candy had taken the car to her storage facility earlier, and a green garbage bag full of ID's sat in plain view on the passenger's seat. It turned out that an employee at the storage facility, knowing that Candy's locker was empty, had called the police after spotting her leaving with a computer monitor that morning. Frightened that she would get arrested -- and, even worse, that our mother would find out -- Candy started talking.

"Once I opened my mouth . . . it was, like, 'God, it's over. Good,'" Candy says. "I felt better the day that I started giving the stuff back than I had felt in a year."

Confessing was almost like a new tweak. For four days, unbidden, she delivered armloads of stolen goods to the authorities. She told our mother that she was visiting the station because she had a crush on one of the officers. In order to bring another cop into the house, she claimed he was an old high school friend.

"I tell you, I was a lawyer, and I was stupid," she says. "I thought that they would just give it back, I would get pretrial intervention, and everything would be fine."

All this time, she continued to shoot up -- even in the police station bathroom. She'd mentioned using meth to the authorities when she was first apprehended; she felt she had to. But the manufacturing didn't come out until a few days later, when, according to the police, they interviewed the boyfriend, and he spilled. (He was jailed; Candy and he haven't spoken since.) Then the arresting officer radioed Candy's "high school friend." Before the DEA showed up that evening, in their hazardous-materials moon suits and masks, the officer sat our mother down and told her about Candy's secret life.

My mother, in turn, told me when I called her that evening -- my 50th birthday -- hurt that Candy had forgotten me.

"Don't be angry," my mother said, her voice thin and tired. "Something's happened."

"Something? What something?" I demanded. "It's my 50th birthday, and Candy can't even call? I have every right to be angry!"

"Candy's been arrested. Methamphetamine." She could barely get the word out.

When meth started gaining a national profile in the late '90s, one of the most frightening things about the drug was its apparently terrible recovery rate: Hardly any addicts, it seemed, ever came back. In February 2000, Serena Altschul, the producer of an MTV documentary on meth, said on "The O'Reilly Factor" that recovered meth addicts were "very few. I met three, and I talked to hundreds, it seems, of users." But new research on meth addiction may paint a less dire picture. One study, led by Richard A. Rawson, associate director of the UCLA Integrated Substance Abuse Program, found that of about 1,000 meth addicts studied in recovery, 57 percent tested negative for meth a year out.

Candy was lucky in that our mother had both the funds and the drive to keep her in rehab as long as she needed it -- almost two years, as it turned out. It took that long because, like other meth addicts, she essentially needed to fix the basic structure of her brain. Meth causes the brain to get flooded with dopamine, the neurotransmitter that drives our reward system. After prolonged use, the dopamine receptors just conk out. Alex Stalcup, the expert in California, likens the scenario to the way an earsplitting concert can lead to temporary hearing loss. The brain needs time to regenerate -- some six to 12 months, says Rawson -- before recovery can even start. Candy "literally couldn't think," she says, for her first year and a half clean. When she got her first job after the arrest, my sister, the former lawyer, had to use a cheat sheet to operate the cash register at Pet Valu.

Listen to Prof. Rawson describe how meth changes the brain's structure in this audio slideshow.

Whatever her hardships were, though, I was in no mood to hear them. The first year after she got caught, I was furious with Candy for what she'd done. The few times I spoke with her by phone shortly after she was arrested, she'd rant: "You're not my guardian! You can't tell me what to do!" While our mother worried about Candy getting thrown in jail, I thought it might be just the thing to straighten her out.

Thanks to her lawyer's efforts, Candy's case was sent out of the standard judicial system and into drug court -- a more forgiving program in which prosecution and defense counsel work with special judges to guide every facet of the convicted addict's life. For someone with Candy's level of confusion, it was perfect. Drug court sent her to two rehab programs and gave her one touchstone person -- her probation officer -- to track her progress, set limits when she needed them and make decisions for her when she couldn't. Fundamentally, it helped her relearn how to live -- even simple tasks, like getting gas, were terrifying at first without a meth buzz.

"I had used external things to try and make me feel like a decent person -- you know, like, 'I am a lawyer' -- but I had destroyed all those external things. So I had nothing to hang on to," she says. "All I had was myself -- and 'myself' was a criminal."

In July 2004, she started looking for permanent work. She applied for a receptionist job at the New Jersey branch of the National Council on Alcoholism and Drug Dependence, an organization dedicated to promoting addiction treatment, prevention and recovery. But the woman who ran the lawyers' assistance program Candy had been attending urged her to go for a policy-analyst opening at the NCADD, instead.

This opportunity put us in our old roles again: nurturing big sister and tentative younger one. Should Candy push herself and go for the high-powered spot, or settle for answering phones and filing? I advised her to seek the receptionist slot. After all, she hadn't been in the work world for four years. I worried that the pressure could send her back to meth. "You don't need to prove anything," I said in a phone call. "You need to take good care of yourself."

Candy was thinking along the same lines. "I was scared that I wouldn't be able to do the job," she says. "I didn't know how much of my brain I had permanently damaged."

But the agency urged her to accept the harder assignment. The fit, it turns out, has been a remarkably good one. Her boss is thrilled with Candy's performance, and Candy is thrilled with her job. Still, she knows she's not home free.

Today, Candy and I are still feeling out our relationship, connecting, long distance, in small ways. We began by exchanging e-mails, short ones to start: "Good morning, Thea. Work is going well today. I'm feeling strong. I love you, Candice." Now, we write to each other several times a day, often joking. "Hi, Candy: This article I'm writing about you is making me crazy. I'm ready to do meth myself! I love you, Thea." "Ha-ha," she shoots back.

There's been another change in our relationship -- one that I would never have anticipated. In the past, Candy was my baby; by mothering her, I could mother myself as well. But these days, Candy can offer me solace, too. When she answers my cell phone call with her gruff, quizzical "Hullo?" I physically relax, knowing she's there for me. That's pretty remarkable, considering how close she came to not being there at all.