House At The edge Of The Park (1980)

Alex is a serial killer driving around New York City at night when he spots a young woman, Susan, moving alongside him. He follows her to a nearby park, where he rapes her before strangling her to death. He then takes her locket as a trophy.

Sometime later, Alex and his friend Ricky are closing the underground garage where they both work, planning to go to a local disco. Before they can leave, a Cadillac pulls in with a young, well-dressed couple, Tom and his girlfriend Lisa, asking for help with their car. Alex refuses to help them, saying the garage is closed, but the slow-witted Ricky decides to help and quickly fixes the problem. Tom tells Alex and Ricky that they are driving to a friend's house in New Jersey for a party and invites them along. Before leaving, Alex stops by his locker, filled with various weapons he uses to murder people, and takes a straight-edged razor.