What is an urban legend? A ghost story? A shared nightmare? Or a way for people to express shared anxieties and pass them down through the generations? Combining the homemade, handheld production values of “Blair Witch Project” with extensive news footage, the documentary “Cropsey” (8 p.m., Investigation Discovery) unfolds like a creepy thriller. And before it’s over, you’ll be hoping it was based on mere fantasy and not lurid facts.
For decades, Boy Scouts and other kids on Staten Island scared themselves silly with tales of “Cropsey,” a legendary man/creature who stole children and dragged them into the woods. The Cropsey legend centered around an old Scout camp and several abandoned asylums, home to rumored underground tunnels, a perfect hiding place for a monster.
Then, beginning in the early 1970s, children and teenagers — many of them mentally disabled — began vanishing. As anguished parents assembled search parties and local media descended on the story, the legend of Cropsey only grew.
Myth met reality when a drifter named Andre Rand, who had worked at a local asylum, was arrested for the murder of one of the children. When her body was discovered buried near his ramshackle campsite, many believed they had found their monster.
“Cropsey” follows the story over several decades, often in the meandering and frustrating pattern of a wild goose chase. We’re taken to graveyards and the demimonde of homeless men who live near Willowbrook State School, a mental institution shut down after a crusading young reporter named Geraldo Rivera made a name for himself in 1972 by exposing squalid conditions.
We learn that Rand worked at Willowbrook and some speculate that his experiences there may have contributed to some vendetta against the mentally ill. Others speculate that he was in cahoots with a Satanic underground, and “Cropsey” follows those allegations to Queens, N.Y., near the ruins of the old World’s Fair site where a woman keeps a vigil to the Virgin Mary. It’s never terribly clear where most of “Cropsey” is really leading, except to one creepy place after another.
But isn’t that what ghost hunts are all about?
“Cropsey” is the first feature-length documentary to air on Investigation Discovery, as part of their quarterly series “ID Films.”
Tonight’s other highlights
• Allison’s rental car appears to have an enchanted radio on “Medium” (7 p.m., CBS).
• Series producer Lisa Kudrow traces her ancestry on “Who Do You Think You Are?” (7 p.m., NBC) and discovers details about her great-grandmother, who died under Nazi occupation.
• Ben Stiller stars in the 2006 special effects-driven comedy “Night at the Museum” (7 p.m., Fox), co-starring Robin Williams, who hams it up as Theodore Roosevelt.
• Superhero imitators meet a family of hard-nosed realists on the season finale of “Wife Swap” (7 p.m., ABC).
• A shooting alters one agent’s life on “CSY: NY” (8 p.m., CBS). New episodes of this series will air in this timeslot beginning on Sept. 24.
• “Lollapalooza 2010” (7 p.m., Fuse) looks at the artists at the music festival.
• An eventful camping trip on “Eureka” (8 p.m., Syfy).
• Fur flies far on “Haven” (9 p.m., Syfy).
• Tom tries to make peace on “Pillars of the Earth” (9 p.m., Starz).