His whole family gathers for Richard Eberneti’s funeral. Among them are Helene, the widow of Brother Richard; Maud, wife of the forever sick brother Timothy, and nephews of the late sisters and brother: George Crossfill, actress Rosamund with her husband-actor and Susan with her husband. Also here is present the youngest sister of Richard - Cora. In her youth, the eccentric girl, who always told the truth at the most inopportune time, became interested in the artist and married him against the will of the family. Her husband had died a long time ago, but Cora had not seen her relatives for twenty-five years and now she came to her brother’s funeral from a small village near London.

After the funeral, lawyer Mr. Entouisl, a friend of the deceased, reads the will. Each of those present receives a good capital. Everyone is surprised at the sudden death of Richard - he was a healthy person. Bowing to the side, Cora asks if her brother was killed. Mr. Enthousl ponders Cora's words. Richard had a son a few months ago who was ill, and his death could ruin his father. The deceased pondered the will for a long time, and met with his relatives. But did he meet with Cora? Perhaps she suspects something.

Relatives of Richard are also interested in the words of Cora. Helene recalls the conversation, and it seems to her that something was wrong.

Mr. Enthuisl decides to go to Kora and talk to her, but he is informed that Kora was killed. The criminal waited until her companion left, climbed into the window, took cheap trinkets in the house and chopped up an ax with Kora, who slept soundly after the trip. Trinkets found near the house. Now the state of Bark will be divided between nephews, but for them it will be a small increase. Her death is not beneficial to anyone.

In the house of Cora, where there is a strong smell of paint, Mr. Entwisle is met by her companion Miss Gilchrist. She shows the canvases that Cora painted herself, and the cheap paintings that Cora bought at a sale. Miss Gilchrist herself understands a little in painting, her father was an artist. Before, she held a small teahouse, but, having gone bankrupt, was forced to go to work. In the house, Miss Gilchrist did light work, they lived with Cora in unison.

Miss Gilchrist reports that Richard recently visited his sister. It seemed to Kora that after the death of his son, his brother began senile dementia - he always imagined killers who wanted to poison him. Miss Gilchrist asks for permission to keep pictures of Cora, especially the one on which the port is painted.

Mr. Entwistle meets with Richard's nephews. They all need money: George Crossfill lost on the stock exchange, Rosamund and her husband want to put on a new play, the Susan family needs their own home. During the assassination, they were all far from Cora's house.

Maud informs Mr. Entwisle that Cora has always been “nuts”, lived in an imaginary world and could let in some kind of parasite like an unemployed musician or artist.

Mr. Entouisl decides to seek help from his friend, the famous detective Hercule Poirot.

Mr. Entwistle calls on Richard's doctor. The doctor is absolutely sure that Richard died his death, and he did not have a suicidal tendency. The servants in Richard's house, too, cannot tell anything. Mr. Entwistle decides to trust Helen. She admits that she feels some kind of trick, but she can not understand what is the matter.

Susan arrives at Cora's house to pick up things. At the same time, an art critic comes there. He wants to look at the paintings, since shortly before his death, Cora informed him that she had bought a good canvas. The critic examines the paintings and says that Cora was mistaken; there is nothing valuable among the paintings.

A wedding cake is sent to the house.Miss Gilchrist thinks this is a package from the daughter of her old friend, whom she forgot. The girl got married and sent her a pie. Susan refuses to eat him, despite the fact that Miss Gilchrist praises him. Miss Gilchrist asks Susan for help: now she is left without work, and it is unlikely that anyone involved in the murder would want to hire. Susan invites her to care for Maud, who broke her leg.

Miss Gilchrist becomes ill at night, and she is taken to the hospital. After examining, the doctor reports that Miss Gilchrist was poisoned by arsenic. Perplexed, Susan recalls that Miss Gilchrist ate the cake she sent. She gives the box of crumbs to the doctor.

A police inspector comes to Susan. After investigating, he finds out that the cake was not delivered by mail.

A police inspector comes to Poirot and they share information with each other. Richard came to Korea. Perhaps he told her something, Miss Gilchrist heard it, and now they decided to kill her?

Under the guise of a representative of a refugee relief organization, Poirot comes to Richard's house to buy him. After talking with the servant and looking around the house, he finds nothing. The servant reports that on the day the master died, the nuns came to collect donations. Richard’s murder is just an assumption, but he hopes to learn something about the murder of Cora. Talking with Poirot, Helene accidentally breaks the ceiling covering the wax flowers on the malachite table and takes the flowers to another place.

Miss Gilchrist works with Timothy and Maud. She has a hard time with Timothy, who is always whimpering, always unhappy, especially since the house has a strong smell of paint due to repairs. She opens the door to the nuns who came to collect donations. At this time, Helen calls and reports that Richard's house has been sold to refugee relief organizations. She invites Timothy to visit his home for the last time. Maud supports Helen: while the smell of paint is in the house, Timothy is better off, and Miss Gilchrist will look after the house, but she fearfully asks to take it with her - she is afraid to be alone.

In the house of Richard, all family members gather, whom Hercule Poirot carefully watches. In a conversation, Miss Gilchrist reports that Cora has always painted her landscapes from nature. This surprises Susan - one of the paintings depicts a port that has long been gone. Cora must have redrawn it from a postcard. Poirot is surprised that Miss Gilchrist was afraid to be left alone in Timothy's house. Poirot asks what she is afraid of, and Miss Gilchrist answers: nuns.

Rosamund and Susan argue over who will get the malachite table. Miss Gilchrist notices that wax flowers look great on him.

Poirot starts a conversation about nuns. Miss Gilchrist seems to be chasing her everywhere - on the day Kora was murdered, a nun also came to the house.

At night, Helen looks at herself in the mirror and begins to guess what was wrong with the behavior of Cora. In the morning she calls Mr. Entwisle to report this, but someone hits her on the head and she faints. The maid finds Helen, and she is sent to the hospital.

Poirot invites all those present to gather in the library and states that Richard was not killed. The detective shares with the inspector information about who was at the time of the murder. The inspector tells Poirot that during the funeral of Richard, nuns came to Cora's house. Nobody opened them, but they heard someone sighing and groaning.

Poirot again gathers those present. The idea of ​​killing Richard came to everyone after a replica of Cora, who always told the truth at the wrong time. But Cora had not been in the house for many years. Nephews do not know her at all, and the rest do not remember well. The famous detective suggests that it was not Cora who came to the brother’s funeral, but Miss Gilchrist, posing as the sister of the deceased. She did this to distract attention from the murder of Cora herself.

But why would Miss Gilchrist kill Cora? Miss Gilchrist's father was an artist, she understands paintings and knows how to draw herself.Seeing that Cora had acquired a valuable painting, Miss Gilchrist poured sleeping pills into her tea, and herself, under the guise of Cora, went to a funeral. The nuns who came heard the sighs and groans of sleeping Bark. In the picture, Miss Gilchrist painted a landscape from a postcard, as Susan noticed, which is why the house smelled of paint. She was going to sell the picture for a large sum in order to purchase a teahouse.

The catch was not suspected, since no one remembered Kora. Cora talked a lot about her childhood, and the stencils, so Miss Gilchrist could indulge in memories. Miss Gilchrist carefully rehearsed all Cora’s manners in front of the mirror, but she didn’t take into account that she would show Cora the other way around. She depicted the habit of Barking her head to one side on the contrary - this seemed strange to Helen. When Helen called Mr. Entwisle, Miss Gilchrist hit her in the head. Fortunately, the blow was not strong, and Helen is already recovering. She prepared the poisoned cake herself, and the nuns who came into the house prompted Miss Gilchrist to think that they were pursuing her. In fact, she wanted to go with Timothy and Maud to find out who they suspected of murder. Mentioning the flowers on the table, Miss Gilchrist betrayed herself - she had been here before and saw these flowers.

Miss Gilchrist is found guilty, but she goes crazy in prison - she is always in a good mood and plans to buy a teahouse.