Sixty years ago, in the spring of 1945, Allied forces liberating Europe found evidence of atrocities which have tortured the world's conscience ever since. As the troops entered the German concentration camps, they made a systematic film record of what they saw. Work began in the summer of 1945 on the documentary, but the film was left unfinished. FRONTLINE found it stored in a vault of London's Imperial War Museum and, in 1985, broadcast it for the first time using the title the Imperial War Museum gave it, "Memory of the Camps."

As the film's history shows, it was a project that was supervised by the British Ministry of Information and the American Office of War Information. And during that summer of 1945 some of the documentary editing was done under the direction of Alfred Hitchcock.

"At the time we found the film, it was not entirely clear what role Hitchcock played in its development," says David Fanning, executive producer of FRONTLINE. "Moreover, one reel of the original six, shot by the Russians, was missing. There was a typed script intact -- undated and unsigned -- but it had never been recorded."

FRONTLINE took the film, added the script and asked the late British actor, Trevor Howard, to record it. The aim was to present the film unedited, as close as possible to what the producers intended in 1945.

"Memory of the Camps" includes scenes from Dachau, Buchenwald, Belsen and other Nazi concentration camps whose names are not as well known. Some of the horrors documented took place literally moments before the Allied troops arrived, as the Germans hurried to cover the evidence of what they had done.

Twenty years after FRONTLINE first aired it, "Memory of the Camps" remains one of the most definitive and unforgettable records of the 20th century's darkest hour.