A stark portrayal of life among a group of heroin addicts who hang out in Needle Park in New York City. Played against this setting is a low-key love story between Bobby, a young addict and small-time hustler, and Helen, a homeless girl who finds in her relationship with Bobby the stability she craves.

When a charming 12-year-old girl takes on the characteristics and voices of others, doctors say there is nothing they can do. As people begin to die, the girl's mother realizes her daughter has been possessed by the devil--and that her daughter's only possible hope lies with two priests and the ancient rite of demonic exorcism.