Walter Huff is a successful insurance agent in Hollywood, and he is a hard-working man. He decides to stop at the home of Mr Nirdlinger to try to convince him to renew his automobile insurance. When he arrives at the home, Mr Nirdlinger is not there, but the maid lets him ins and he ends up speaking with Phyllis Nirdlinger, his wife. Walter is attracted to her immediately but thinks that she looks weary; from life? From her marriage? He doesn't know, but he finds her intriguing. They chat casually and she asks him in a round-about way about the possibility of taking out accident insurance. He returns to the home a few days later, and this time, Mrs Nirdlinger gets more specific; she wants to know if it is possible for her to take out an insurance policy for her husband without him actually knowing about it.
Walter begins to see where the conversation is going, and that it is taking a rather dangerous turn, and for a second, he considers leaving, but he has started to fall hard for Phyllis Nirdlinger. He kisses her, and the two begin building a flirtatious relationship, and at the same time plotting the death of her husband for a fifty thousand dollar insurance pay out.
Walter uses all of his tried and tested selling tactics on Mr Nirdlinger, convincing him to purchase the life insurance policy and suggesting that he keeps it a secret from his family. Nirdlinger is open to purchasing the policy but does not want to keep it a secret from his wife and step-daughter, Lola. Mr Nirdlinger prevails, and in the end Phyllis and Lola act as witnesses when the insurance contract is signed. This makes Walter very uncomfortable, knowing that Nirdlinger signing the policy is the first step in a dastardly murder plot, and does not like the fact that they have involved Lola in her step father's murder.
Walter and Phyllis decide that they should make it appear that Nirdlinger has died by falling out of a moving train. They plan the crime itself, and Walter plans a meticulous alibi for himself so that there is no way he can be connected to the actual murder that Phyllis is going to commit. Phyllis kills her husband and then puts his body in the family car, driving to the train station and meeting Walter, who is by now disguised as her husband; they have decided that the death will seem more feasible if Walter is seen alive and well on the train beforehand. Walter allows himself to be noticed briefly by a couple of employees, and by some fellow passengers. As the train begins to move, he jumps from the back of it when it reaches a pre-determined meeting spot, where Phyllis is waiting for him. They then dump the body of the real Mr Nirdlinger.
The following day, news of the death has spread. Walter's insurance company have begun their standard death investigation and just as Walter predicted, when Phyllis goes to file her claim, the insurance company refuse to pay out. Phyllis hires an attorney but still calls Walter constantly for advice about how to act and what to expect. Walter is worried when Lola comes to his office to share her feelings of disquiet with him; she explains that Phyllis was her mother's nurse, and that her mother died from pneumonia in the winter, in a chilly cabin. She believes that Phyllis killed her mother in order to start a relationship with her father, and now she has the same concerns about Phyllis's role in her father's death. he is planning to create a scene in court, hoping to trap Phyllis into confessing or at the very least, saying something that will implicate herself. Walter is hopelessly in love with Lola, and wants to protect her from the truth about her father's death, so he decides to kill Phyllis and arranges to meet her in the park where he intends to do the deed; however, Phyllis has already turned against him, and has paid an assassin to murder him.
Walter survives the attempt on his life, but barely. He is taken to hospital and when he wakes up finds his boss standing beside his bed. He confesses to his role in the murder, and offers to send a signed confession from South America, implicating Phyllis. However, there is a spanner in the works when he runs into Phyllis on the boat that is supposed to be taking him to safety and anonymity in Mexico. Phyllis tells him that Lola has married her boyfriend, and almost simultaneously both Phyllis and Walter realize that they have absolutely nothing, no love, and nobody to share their lives with. They also realize that they will both be arrested soon, and they commit suicide by jumping over the side of the boat together.
