Dead Man's Seat(1984)

Original title: O Lugar do Morto

A newspaper reporter comes across a man and woman arguing on the beach, and after obligingly driving the woman around when she seeks him out, he takes her back to discover that the man has been murdered. The woman takes off, but the reporter, after many twists and turns, runs into her on a train. They start a relationship, but he had better pay closer attention to how he got to know her in the first place.