***SPOILERS*** It was gangster Danny Mott's big mistake to try to strangle and drown, in the swimming pool at his spa, cigarette girl Julie Mathews that brought insurance investigator Mike Barnett into the case. It turned out that Julie had photographic evidence that Mott has been cheating on his tax returns and was using it to blackmail him. With Barnett finding the camera at a local pawn shop that Julie used to take photos of Mott's books he unknowingly exposes the film making it useless to use against Mott in a court of law.
Still Mott not knowing that the evidence against him is non existent he tries to murder Julie who as it turns out already killed herself by jumping off the George Washington Bridge or so that's what at first it looked like. It's soon after that Julie reappears at the spa no less giving Mott a second chance to murder her only this time Barnett is there to stop him. The jerk-Danny Mott-doesn't know that the evidence against him has-the film- been unknowingly destroyed by Barnett who makes him think that it wasn't.
Barnett for his part put his life on the line by confronting a well armed, with a .38, Mott to get him to confess not only on his attempted murder of Julie but his cheating the US Government of it's some $200,000.00 in back taxes that he owes it. And for that Mott not only loses his freedom but his life as well by being shot in self defense, of course, by Julie when Barnett tried to wrestled Mott's gun away from him.