Sleepaway Camp (also marketed on VHS as Nightmare Vacation) is an American 1983 exploitation slasher film written and directed by Robert Hiltzik, who also served as executive producer. The film tells about a young girl and her cousin sent to a summer camp, where a group of killings begins shortly after their arrival. The film came at a time when slasher films were in their heyday, and is largely known for its twist ending, which is considered by some to be one of the most shocking endings among horror films. Sleepaway Camp is also notable as the last movie of Tony-nominee Mike Kellin, and as the film debut of Christopher Collet. Sleepaway Camp received positive reviews from critics, with many critics praising the film's twist ending.
(Summary from Wikipedia)