Ghost (1990)

Sam and Molly are a very happy couple and deeply in love. Walking back to their new apartment after a night out at the theater, they encounter a thief in a dark alley, and Sam is murdered. He finds himself trapped as a ghost and realizes that his death was no accident. He must warn Molly about the danger that she is in. But as a ghost he can not be seen or heard by the living, and so he tries to communicate with Molly through Oda Mae Brown, a psychic who didn't even realize that her powers are real.