We Are Here — Michael Marshall

It should've been the greatest day in David's life. A trip to New York, wife by his side, to visit his new publisher. Finally it looks as though the gods of fate are going to lift him from schoolteacher to writer. But on his way back to Penn Station, a chance encounter changes all of that. David bumps into a stranger who covertly follows him, and then, just before they board the train home, passes him by close enough to whisper: "Remember me."

The stranger follows them back to where they live, and it isn't long before David realizes that this man wants something from him...something very personal, that he may have no choice but to surrender.