Growing up on Staten Island, filmmakers Joshua Zeman and Barbara Brancaccio had often heard the legend of Cropsey -- the escaped mental patient who lived in the old abandoned Willowbrook Mental Institution and would come out late at night to snatch children off the streets. They just assumed Cropsey was an urban legend, but that all changed in the summer of 1987 when a 13-year-old girl with Down syndrome, named Jennifer Schweiger, disappeared from their community. Now as adults Joshua and Barbara have returned to Staten Island to create Cropsey, a feature documentary that delves into the mystery behind Jennifer and four additional missing children and uncovers a reality that is more terrifying than any urban legend.