The Guardian (1990)

Alan and Molly Sheridan have a baby boy named Jake. They hire a baby-sitter, Camilla, to look after Jake and she becomes part of the family. The Sheridan’s friend and neighbour, Phil, takes a liking to Camilla and asks her out. She refuses, but Phil follows her and discovers that she is not quite human. Camilla discovers that she has been followed and Phil is pursued. He leaves a desperate message for Alan and Molly which reveals that Camilla has special plans for baby Jake.