THE STORY of the Willowbrook State School is terrifying enough: Built as an institution for mentally handicapped children, it was exposed for abuses ranging from medical experiments to sexual abuse. The Staten Island facility now sits empty, save for the drifters, former patients, and Satan worshippers rumored to be living in its network of tunnels. Filmmakers Barbara Brancaccio and Joshua Zeman were among the generations who grew up with stories of "Cropsey," supposedly an escaped patient who kidnapped and killed children on the grounds. The tale was typical of those meant to ward off kids and teenagers from such places. The difference—as they found out when the corpse of a missing 12-year-old girl showed up there—was that this story was, at least partially, true.

Brancaccio and Zeman have the benefit of their film's most compelling footage having already been taken. Images of the school while it was still operating are more nightmarish than their own shaky-camera forays onto the grounds at night. What they've added, though, are interviews with area residents that illustrate the degree to which a string of unsolved child disappearances—almost always children with mental handicaps—has permeated the identity of the community.

Despite a lack of physical evidence, the man serving time, the presumed "Cropsey," is Andre Rand. He's a compelling villain: A former employee of Willowbrook who did indeed squat and camp on its grounds, his scrawled, rambling correspondence with the directors during filming certainly does not make a case for his mental stability, though he also clearly takes pleasure in taunting people with the possibility that he holds the answers to the missing children's fates.

The lack of closure for the victims' families is wrenching, but Brancaccio and Zeman don't seem to possess any particular expertise with which to analyze the mysteries. They've simply done a sufficient job laying out the haunting pieces of a picture worthy of fueling the nightmares of many generations to come.