A Blueprint for Murder (1953) - Plot Summary Poster


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  • Whitney Cameron suspects his sister-in-law has poisoned his brother and niece, but without proof how does he prevent the murder of his nephew?

  • Two orphans, Polly and Doug, live with their stepmother Lynne; Polly collapses with the same mystery symptoms that killed her father. The kids' visiting uncle, Whitney Cameron, is warned that the symptoms match strychnine poisoning, but that poisoners are seldom detected and rarely convicted. Sure enough, no case can be made against the obvious suspect; so what can Whitney do to save the next victim?

  • Whitney 'Cam' Cameron returns to Manhattan to visit his widowed sister-in-law Lynn and her stepchildren, his niece and nephew. His niece has suddenly fallen ill with a mysterious malady whose symptoms mirror those of his deceased brother. After being hospitalized, the girl seems to be rallying but quickly takes a turn for the worse and dies from the undiagnosed illness. Cam's friend and lawyer Fred Sargent and his wife Maggie believe that the symptoms may suggest strychnine poisoning, and as Lynn stands to inherit a fortune if nephew Doug dies also, Cam now views her with suspicion. Despite circumstantial evidence that she murdered her step-daughter, Lynn is released for insufficient cause. When she tells him that she intends to take Doug to Europe, Cam realizes that desperate measures are needed if he is to save the boy's life.


The synopsis below may give away important plot points.


  • Young Polly Cameron is rushed to the hospital, accompanied by her stepmother Lynne. All the while she is screaming "Don't touch my feet!" Doctors cannot pinpoint the cause of her illness but believe she was poisoned. The following morning her uncle, Whitney Cameron (known as Whit), arrives at the hospital. By this time Polly is stable. Lynne asks Whit if he can stay for a while to spend time with Polly and her younger brother Doug. Whit agrees and later stops by to visit his friends, Maggie and Fred Sargent. Fred is the family attorney and Maggie is a journalist. When Whit mentions Polly's strange symptoms and how she did not want her feet touched, Maggie is reminded of a case long ago. She promises to do some research. Whit is not really concerned because Polly is recovering.

    That night Whit has dinner with Lynne and Doug. He suggests that Doug spend the upcoming summer with him. Lynne initially agrees. Then the hospital calls. Polly has had a relapse. By morning she is dead.

    Whit again visits the Sargents. Maggie has information about a man who died from strychnine poisoning. He kept saying "Don't touch my hands!" She suggests that Lynne may have poisoned Polly. Whit scoffs at the idea, mentioning how close Lynne was to the children and how well she treated them. Maggie points out that history has had other female murderers who were like Lynne: cultured, beautiful, and intelligent. Whit finds himself becoming suspicious. Fred points out that under the terms of Whit's brother's will, Lynne has only a small income. She would not inherit the entire estate unless both of the children died.

    Lynne decides to take Doug to Europe for a year instead of letting him spend the summer with his uncle. There is nothing that Whit can do to prevent it, since his brother's will gives custody to Lynne. Whit talks to the doctors and nurses who took care of his niece. The child received only medication from the hospital pharmacy. Lynne refused to permit an autopsy. She wanted the child cremated but Whit talked her out of it. He felt it was not what his brother would have wanted.

    By now the Sargents and Whit fear for Doug's safety. They are afraid he will mysteriously die while in Europe. Polly's body is exhumed for an autopsy. Whit conceals this from Lynne until the results are in. Polly died of strychnine poisoning.

    The police interview the servants and Lynne but come up with nothing. No one would admit to giving Polly anything to eat on the night she took sick. Lynne is very cooperative and even suggests hiring a private investigator. Whitney discovers that the pills given to Polly on the day she died were from a different pharmacy, since the one at the hospital was closed. Lynne was on her way home to pick up some things for Polly and offered to have it filled. There seems little doubt that she was involved. She is furious when she learns that Whit is behind the investigation. After interviewing her again, the police arrest her and a hearing is held to see if their is enough evidence to charge her.

    Doug is told nothing of what is going on. The Sargents take care of him until the hearing is over. There simply isn't enough evidence for a conviction and Lynne is free to go. Whit tries and fails to get emergency custody of Doug. He knows of only one way to keep Doug safe and that is to kill Lynne. He purchases a bottle of rat poison. The store clerk shows him the same thing in tablet form. Whit notices how they look just like aspirin tablets except for the "W" stamped on each one, to represent the company that manufactured them.

    Whit books passage on the same ship that Lynne and Doug are on. Once in his cabin, he pours the rat poison into a different bottle and conceals it a pocket. He still isn't sure if he can carry out his plan. Doug is pleased to see Whit but Lynne is not. Whit apologizes to her for all that happened and sweet-talks her, giving her the impression that he is interested in her romantically. Later he loses his nerve and tosses the bottle of rat poison into the sea.

    On the last night of the voyage, Whit goes to Lynne's stateroom to retrieve her coat. On an impulse he goes into the bathroom and checks her toiletries. To his shock, her bottle of aspirin contains three of the "W" tablets he had seen earlier. He realizes his suspicious were correct all along and that he must quickly come up with a new plan.

    After a last walk around the deck, Whit and Lynne return to her cabin. They kiss and he orders drinks from the bar. Behind Lynne's back he dissolves one of the "W" tables into her drink. She complains of the bitter taste and Whit says his is bitter too. After she finishes the drink, he tells he what he did and that she only has a few minutes before the poison takes effect. Lynne angrily denies having anything to do with Polly's death and says the "W" tablets are from an old bottle that she combined with a new bottle. Whit reminds her of the ticking clock and that she can still be saved. She orders him to leave and goes into her bedroom. To her shock a man is sitting there. He identifies himself as the ship's detective and that Mr. Cameron called him to witness the conversation. The men wait as the minutes tick by. Lynne shows no symptoms of having been poisoned. The detective is confused and asks Whit if he had really given this woman strychnine. Whit replies that he gave her a pill from her aspirin bottle.

    After ten minutes pass and Lynne is still fine, she orders them to leave. The detective tells Whit that he will have to write up a report of the evening's events. Whit goes out on deck, shocked that the "W" pill hadn't been strychnine after all. Polly's death must have been caused by a careless pharmacist giving her the wrong pills. Then he is summoned to the ship's doctor's office. Lynne had called them and they just managed to save her life.

    Back in New York, Lynne is tried and convicted for the murder of her stepdaughter. She receives a life sentence. The final scene shows the Sargents waving goodbye as Whit and Doug board a plane.

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