Miss Marple, an elderly lady, is resting in a hotel on the Caribbean coast. Her interlocutor, Major Palgrave, babbling about all sorts of trifles. Among other things, he talks about a serial killer who killed his wives. Accidentally, the major in the wallet is a picture of the criminal. Looking for a picture, the major accidentally sees something behind Miss Marple, changing in the face and moving on to another topic.
To Miss Marple are two suited couples in the hotel – Colonel Hillingdon with his wife Evelyn and Greg and Lucky Dyson. Soon the hotel hosts Tim and Molly Kendalla, who sat nearby and checked account books. Taking advantage of the fact that everyone is keen on the conversation, Miss Marple turns around, but does not see anyone behind her.
In the morning Miss Marple learns that Major Palgrave died suddenly at night. He abused alcohol, took medicine for the night, death came from increased pressure. She decides to ask for a photograph of the killer who was in the wallet with the major, stating that this is the only snapshot of her deceased nephew, but the picture has disappeared. Miss Marple does not believe in the official version of the major’s death.
Miss Marple ponders what happened. She realizes that the major saw the same killer, but from the men there were Colonel Hillingdon, Mr. Dainos and the servant of the resting millionaire Rafael Jackson. She decides to conduct an investigation.
Victoria’s maid tells Molly
Miss Marple gathers information about the people she is interested in. Jackson works for Mr. Rafiel for about a year. He is not married and knows how to have a good time. Greg Dyson is married to Lucky for several years. His first wife, cousin Lucky, died a few years ago on this island, after Greg changed her from Lucky. Colonel Hillingdon is a calm, pleasant man, but he does not have the best relations with his wife.
Dr. Graham is worried about Molly. She is always nervous, she has nightmares. The woman takes sleeping pills to calm down, but the pills make it worse. He shares his experiences with Miss Marple, and the elderly lady tells the doctor about her suspicions.
Victoria gives Greg Dyson a bottle of pills, which was found in the room of the major. After his death, the girl was told to throw out all the medicines, but Victoria knows that the pills belong to Greg. Surprised, Greg does not understand how his tablets could get to the major. Victoria believes that someone has put them.
Mrs. Hillingdon complains to Molly that her husband is not indifferent to Lucky Dyson. A woman is ready to kill her rival out of jealousy. Molly says that she has recently had a memory failure. She hears some voices, steps. Tim finds out about this and tries to protect her.
Colonel Hillington admits to his wife that he wants to leave as soon as possible, otherwise he will kill Lucky. Once Lucky asked him to buy something in the pharmacy and rewrote a prescription for this. The first Greg’s wife took the medication and died. Lucky motivated this by saying that a woman is seriously ill, and death will save her from suffering. Now Colonel Hillington hates the woman he once loved. Evelyn believes that they should stay and behave as usual.
Evelyn tells Tim that Molly needs to be shown to the doctor. Tim does not agree, he believes that there is no danger, Molly simply upset the death of Major Palgrave. Calling her family makes no sense, since Molly broke with her family, mother and sisters. Their conversation is interrupted by Molly’s cry: she found Viktoria, stabbed in the bushes, in the bushes.
Victoria’s husband tells the police that his wife had demanded money for silence.
Greg Dyson tells the police that Victoria found his bottle of pills. He thinks that Victoria knew something.
One of the chefs reports that he saw Molly with a knife in his hand. Tim replies that she checks the instruments on the tables. Perhaps she was carrying a knife that the waiters forgot to put. Molly does not remember if there was a knife in her hands. The police can not find a suspect and comes to a standstill.
Miss Marple shares her suspicions with Mr. Rafiel and asks him, as an influential man, to help. The major recognized the serial killer. Since he spoke loudly, the killer could hear and put pills to him. Mr. Rafiel heard from the police inspector that an exhumation had been carried out and a poison was found in the body of the major. But why kill the killer major, if he has no proof? Probably, one more murder is planned.
About those whom Miss Marp suspects, Mr. Rafiel does not know anything. His servant Jackson does not look like a killer either. The millionaire tells Miss Marple that Jackson gets a good salary, but after his death he will not get a penny. Nothing will be received by his secretary, Esther Walters, a young widow with a child. Mr. Rafiel believes that Jackson is not indifferent to Esther. To their conversation, Esther joins, but she does not know anything about the murderer and the death of Major Palgrave.
Talking with hotel guests, Miss Marple learns the story of Molly. Once the girl met a man. Her mother found out something unpleasant about him and told him to bring him home, but Molly refused. Miss Marple notices that the hair color of Lucky and Molly is the same, only in Molly is it natural, and Lucky’s hair colors.
Suddenly Miss Marple notices how Jackson secretly makes his way into Mr. Rafiel’s room, although he must now be near his master. After following him, she sees Jackson rummaging through the papers.
At night, Tim awakens Evelyn and asks her to look after Molly, who took a lot of sleeping pills. Evelyn is succeeded by Miss Marple. The elderly lady worries: Molly complains that she can hear footsteps and voices, maybe she is being pursued by a man her family did not want? Tim waved it away, it’s a long time ago.
Taking care of Molly, Miss Marple finds a book about nervous illnesses under her pillow. The book is open on that page, which describes the mania of persecution and schizophrenia. Seeing Molly asleep, Miss Marple leaves her and goes to look for Dr. Graham. She sees Jackson coming into Molly’s room. Miss Marple finds him in the bathroom with a box of cream in her hands. Once he worked as a pharmacist and wondered what kind of cosmetics women use. He heard that sometimes drugs are mixed in cosmetics. Miss Marple decides to pass the box of cream to Dr. Graham.
Esther Walters believes that Molly experiences because of her husband’s indifference to her and decided to attract his attention, but she still loves the man her family rejected.
The next evening Tim tells Miss Marple that Molly has almost recovered and tomorrow will rise. At night, Miss Marple wakes up from the noise: Molly disappeared. Tim finds a wife lying in a creek face down. But Miss Marple, who approached, notices that the dead woman is not Molly, but Lucky. The hair color is the same, but the roots show that the hair is dyed.
Miss Marple again recalls the day when Major Palgrave talked about the murderer. Suddenly it dawns on her: one major’s eye was glass. Miss Marple asks Mr. Rafiel for help: she must prevent the murder. To do this, she needs Jackson.
Molly returns to her room. Shocked by the murder of Lucky, she keeps repeating that it was not she who killed her. Tim tries to calm his wife and gives her a glass of water. At this point, Jackson takes the glass from his hand. Miss Marple and Mr. Rafiel and Esther enter the room.
Miss Marple clarified the situation: she had always believed that Major Palgrave was looking to the right. However, because of the glass eye, he saw only what is on the left, and there sat Tim Kendall. Hearing the conversation about the killer, Tim tossed him pills. Victoria saw this, began to ask him, and Tim killed her. But most importantly, he planned to kill Molly.
Esther interrupts Miss Marple’s story, rushes to Tim and yells that this is not true.
Tim convinced Esther that Molly loved another man. She expected Tim to divorce Molly and marry her. From his friend Jackson, he learned that, according to the will, Esther would receive a large sum after the death of Mr. Rafiel. Molly, seeing that her family opposes her relationship with a man, played a parting with Tim, and he appeared before her relatives under a different name.
With Molly’s money, they bought a hotel. Here Tim met Esther and decided to get her money. Molly, he suggested that she was ill, slipping her book about mental illness. Jackson guessed what was happening and decided to look at Molly’s cream. In the cream, a drug is found, causing memory dips. Convincing his wife that they must hunt down the killer at night, Tim lured her out of the house, but mistakenly drowned Lucky.