In Double Indemnity, the classic film noir by Billy Wilder, Walter Neff (Fred MacMurray) is an insurance salesman who conspires with Phyllis Dietrichson (Barbara Stanwyck) to murder her husband and collect on an accident policy. Walter is good friends with Barton Keyes (Edward G. Robinson), an investigator with the same company who has an uncanny ability to spot a phony claim. As a result, Walter knows all the angles and he and Phyllis almost manage to commit the perfect crime.
In the beginning, Phyllis tries to get Walter to allow her to get accident insurance on her husband without his knowing about it. She hates her husband, but has no definite plan to murder him. She is just hoping that once she gets the policy her husband will have an accident in the oil fields and die. We later find out from her stepdaughter Lola (Jean Heather) that Phyllis may have contributed to her mother’s death while acting as her nurse during an illness. According to Lola, while her mother had a fever, Lola walked into the bedroom and found that Phyllis had the windows wide open letting in the cold winter air. After the mother died, Phyllis then married Lola’s father. This kind of opportunism is probably what Phyllis had in mind for her husband once she got him the accident policy: wait for propitious circumstances, and then help them along a little.
At first, all Walter was hoping for was to have an affair with Phyllis. But when he hears about her plan to get the accident policy on her husband without his knowing about it, Walter immediately realizes that she is dangerous, and he gets up and leaves, picking up his hat as he heads for the door. There follows a scene that many people miss, while others catch it but think it is a goof. That night, as Walter broods over his situation with Phyllis, she shows up at his apartment. When he opens the door, she says, “You left your hat today.” A lot of people, including professional critics, think that Walter did leave his hat behind at her house. Others, having noticed that Walter picked up his hat on the way out the door, conclude that this is a mistake. However, it is obvious that Phyllis has no hat in her hand as she stands in the doorway.
What Phyllis is doing is amusing herself with the remark about the hat. If a man has recently met a woman and would like to see her some more, he may pretend to leave something behind at her home. We don’t wear hats so much any more, but an umbrella is a good substitute. Then the man can call her up the next day and say, “Did I leave my umbrella over at your place yesterday?” When she says that he did, he can then ask if it would be all right to drop by and pick it up. With a little luck, one thing will lead to another. Phyllis is alluding to that ruse by making believe she has his hat and is using it as an excuse to see him. In so doing, she is essentially saying, “We both know why I’m here.”
On the night she and Walter trick her husband into signing the application for the accident insurance, Walter hears him say he is taking a trip to Palo Alto. Walter tells Phyllis to get him to take the train. He knows that dying while riding a train is so rare that the $50,000 policy will pay off at twice that amount owing to a double indemnity clause in the policy. Just to put things in perspective, $100,000 in 1938 (when the story takes place) would be almost $1,700,000 today. They kill her husband before he gets on the train. Then Walter pretends to be the husband and boards the train, jumping off soon after, before the train can pick up much speed. Then they dump the husband’s body on the tracks.
The coroner rules it to be an accident, and so the police do not bother to investigate any further. But the insurance company is on the hook for the $100,000, and so Keyes starts looking into the matter, especially after he gets one of his hunches. James M. Cain, who wrote the book this movie was based on, also made an insurance policy part of the plot in the The Postman Always Rings Twice, which was made into a movie in 1946. Normally, if the beneficiary of a policy is charged with murdering the policyholder, the insurance company will delay paying the claim: if the beneficiary is acquitted, they will pay; if he is convicted, they will not. In this movie, however, it is the other way around. The prosecutor waits to see what the insurance company’s investigators come up with. When these top-notch investigators fail to find incriminating evidence, the insurance company pays the claim. That is when the prosecutor realizes he doesn’t have a case. Finally, an insurance investigator solves a crime in The Killers (1946), because his company had to pay off when the money stolen was never recovered. In other words, insurance money supplies a motive for the investigation in all three movies. In a similar way, money is also the motive in films noir in which a private detective solves a crime when the police failed to. So, instead of the police solving the crime as part of their duty to enforce the law, films noir cynically reject this idealistic notion by making money the central motive of the investigation rather than justice.
Suspecting that Mr. Dietrichson was murdered, Keyes realizes it would be easier to murder him before he got on the train, which is what happened, rather than kill him on the train. That means that Phyllis must have had a male accomplice to pretend to be her husband. He starts having her house watched. As a result, Walter and Phyllis have to stop seeing each other until the investigation is over. Phyllis’s stepdaughter, Lola, had a boyfriend, Nino Zachetti (Byron Barr), but they broke up, and soon he and Phyllis start having an affair. Keyes concludes that Nino is the accomplice in the murder and calls off the surveillance. He tells Walter he is going to reject the claim, daring her to take it to court.
What follows from this point on seems to make no sense. Walter goes over to Phyllis’s house intending to strangle her, and she slips a pistol under the cushion so that she can murder him. Let us consider the situation from Phyllis’s point of view. Unless we assume she is psychic, she does not know of Walter’s plans to kill her. So, what does she hope to gain by killing Walter? The police have already dropped the case, but if Walter is murdered, the police will not only investigate his death, but it might make them reconsider her husband’s death as well, since Walter sold her the policy. Furthermore, shooting Walter in her house will not only get blood all over the place, but she will then have to dispose of the body. What is she going to do, cut him up in the bathtub like the guy in Rear Window (1954), and then make several trips to the city dump with the body parts in a suitcase?
The prudent thing for her to do is to just sue the insurance company. If she wins, she can give Walter his cut and all will be well. If she does suspect Walter wants to kill her, then she should simply refuse to let him come over to her house. After all, he is not going to gun her down on Main Street. Therefore, it makes no sense for her to shoot Walter.
Now let us look at it from Walter’s point of view. By this point, Walter has obviously given up on getting his share of the money, because she cannot very well collect and split with him if she is dead. So, what does he hope to gain by killing Phyllis? All Keyes knows is that Phyllis has been seeing Nino, which means she has been having an affair with a younger man. Big deal. He says he has investigated Nino’s movements on the night of the murder, and they cannot be accounted for. We later find out from Lola that he broke a date with her the night of the murder, claiming he was home sick. But that is not exactly evidence that he committed a murder. In any event, we know that Nino did not do it, so he is not likely to get tripped up in a cross examination in court, as Keyes seems to think. With nothing more to go on, Keyes has little chance of successfully denying Phyllis’s claim in court, and it certainly would not be enough for the police to reopen the case. Walter should just quit having anything to do with Phyllis.
But let us assume that beyond all reason, Walter is afraid that enough would come out in the civil suit that would lead the police to reopen the investigation into the death of Phyllis’s husband, and make them to suspect not Nino, but Walter. In that case, Walter should simply turn in his resignation at the insurance company and go to Mexico for a while. If Phyllis’s lawsuit does not lead to a new police investigation in which he becomes a suspect, he can always return to the United States later; if it does lead to a new investigation and he does become a suspect, he can continue to hide out in Mexico. But his killing her will definitely cause the police to investigate. Walter’s plan is that Nino will be blamed for Phyllis’s murder. But Nino might have an alibi for that night. As it turns out, Nino was coming to see Phyllis just as Walter was leaving the house, but Walter could not know Nino was going to do that. Walter tells Phyllis, just before he kills her, that he knows Nino will be coming to see her in fifteen minutes with the cops right behind him, because it has been all set up. Now, how would he know that? Furthermore, Nino would have no motive for murdering her. If anything, the police might end up suspecting Walter. Therefore, it makes no sense for Walter to murder Phyllis.
However, it is reasonable to assume that two people who have committed a murder and are afraid of getting caught might not be thinking clearly. Each one might suppose that killing the other one would make them safe, because then there would be no accomplice to testify against them. So, their behavior might make sense on an emotional level.