England, the beginning of the thirties. Hercule Poirot with his old friend and assistant captain Hastings arrives at the seaside resort of St. Louis in the south of England. Near the Majestic Hotel where they are staying, they meet a young girl, Nick Buckley. In a conversation over a cocktail, it turns out that she is the owner of a house standing on the edge of the Endhouse. Nick Buckley informs unconditionally that over the past three days, three times escaped certain death.
In a simple felt hat Nick, forgotten at the table of random acquaintances, there is a round hole with smooth edges - a clear trace of a bullet. Poirot takes the hat to a girl having dinner with friends - reckless captain Challenger, blond handsome Jim Lazarus, antique dealer, and "tired madonna", blond Frederica Rice. Poirot agrees with Nick about his visit to the Endhouse.
Intrigued, Nick is hosting Poirot and Hastings. The endhouse turns out to be moody, old, in need of renovation. Poirot shows Nick the bullet he found in the park, and this makes her believe that someone is encroaching on her life. At the request of Poirot, Nick lists all the troubles that have happened to her recently: the picture hanging over her bed fell in a heavy frame; when she went down the path to the sea, she was nearly killed by a broken boulder; the car's brakes failed. Guests will find out that the name, more precisely, the nickname the girl received in honor of her grandfather, Old Nick. Her real name is Magdala, it is often found in the Buckley family.
At the end of the conversation, learning that she was shot from a Mauser, Nick is looking for a weapon inherited from her father, but does not find. This makes her take Poirot's warnings more seriously. At the request of the detective, Nick talks about his inner circle. In addition to friends, this is the servant Ellen, her gardener husband, their child and a couple of Croft from Australia, whom she rents outhouse. Nick also has cousin Charles Weiss, a local lawyer.
Following the advice of Poirot, Nick by telegram calls from Yorkshire his same age cousin Maggie, according to the girl, "too sinless." As if by chance, Poirot asks if Nick ever made a will, and finds out that six months ago, lying down on an appendicitis operation, Nick bequeathed Endhouse to cousin Charles, and everything else to Frederica Rice, whom her friends call Fredley.
In the evening at the hotel during the dances Poirot tells Frederica that Nick was shot. Fredley, who believed that a friend invents all her accidents, is shocked. Poirot and Hastings meet Croft and, at his request, go into the wing to meet his bedridden wife after a train accident. Croft unusually (even too) friendly and too intrusive emphasize their "Australia".
Nick comes into the hotel to Poirot to show a telegram informing about the arrival of cousin Meggie. Her appearance is lively, but dark circles under her eyes. It is evident that anxiety eats her. Poirot suggests that the girl is worried not only because of the assassination attempts committed on her. Nick invites Poirot and Hastings to the Endhouse to watch the fireworks.
Guests gather at the Endhouse: Freddy, Lazarus, Poirot with Hastings. Here is the recently arrived cousin Nick, Maggie, in an old black evening dress, without makeup. She sincerely wonders who needed to encroach on Nick's life.
The hostess herself appears - in a black dress just received from a tailor, with a bright red Chinese shawl thrown over her shoulders. For cocktails, it comes to Michael Seton, a brave pilot who single-handedly traveled around the world on an Albatross amphibious aircraft and disappeared a few days ago. Hope that he was alive, almost gone. It turns out that Nick and Freddy were familiar with him.
Nick leaves the phone and is absent for a long time. Reappearing, she calls everyone to watch the fireworks. The spectacle is magnificent, but a piercing wind blows from the sea. Poirot, afraid of catching a cold, decides to return to the house. Hastings follows him. Not far from home, they see a body spread out on the ground in a bright red shawl. Poirot blames himself for this death. Nick appears in the doorway and cheers at the cousin. Poirot turns the body over - it turns out that Meggie Buckley is killed. She died instead of Nick - she, leaving for a jacket in the house, left her her shawl. Nick is in shock. She is put in a private hospital. To protect Nick from possible assassination attempts, doctors at the request of Poirot forbid meeting with her.
Poirot analyzes the situation. He writes a list of all "actors" and considers the motives and suspicious circumstances associated with each of them. Hastings falls asleep in an armchair from fatigue, and the last thing he sees is Poirot throwing the crumpled sheets into the paper basket.
When Hastings wakes up, Poirot sits in the same place, but his eyes cast a cat's gleam - this is a sure sign that Poirot has guessed something important. And in fact, the detective solved the mystery of Nick, and a visit to the hospital confirms his hunch.
Nick was engaged to the deceased pilot, Michael Seton. The engagement was kept secret because of Uncle Michael, old Sir Matthew, a rich man, an eccentric and a woman-hater. Michael’s successful flight would have made Sir Matthew fulfill any nephew’s desire, including agreeing to get married. But during the flight of Michael, his uncle had an operation, and he soon died. Before leaving, Poirot asks Nick for permission to look for her will, and she allows him to "inspect anything."
At the Endhouse, Poirot speaks with the maid Ellen, and she mentions the existence of a hiding place in the house, and also reports that before the tragedy she had a bad feeling about her. From the letter Freddy Rice found by the detective, it becomes clear that she is using drugs (Poirot already guessed this by changing her moods and strange detachment).
In the dresser, the detective finds Michael's letters. The letters here are clearly not all. From the last letter it becomes clear that Michael, without bothering with formalities, wrote a will on a piece of paper, leaving all his property to the bride.
Poirot and Hastings return to the hospital. Nick denies the existence of a cache. But he recalls that Croft, who had advised her to make a will, volunteered to omit the letter. So the will must be with Charles. But he is not in the lawyer's office.
Croft vowed to confirm that he had omitted the letter, and his wife was touchingly worried about Nick. But this does not prevent Poirot from tearing a piece of newspaper, on which there remained a greasy trace of Croft's thumb and forefinger.
Maggie's parents come to pick up the body. These are charming, simple-minded old people, dejected by grief and full of sympathy for Nick.
From a conversation with the lawyer of the Seton family, Mr. Whitfield, Poirot makes it clear that Nick must receive a huge amount. Poirot and Hastings return to St. Louis. Calling the hospital, the detective finds out that Nick is dangerously ill. She has cocaine poisoning. She ate a candy bar stuffed with dope. Nick violated Poirot’s prohibition not to touch the food sent, because the card “Greetings from Hercule Poirot” was attached to the box (exactly the same he sent Nick with a bouquet of carnations). Cocaine in sweets puts Frederick Rice in suspicion. In addition, in the missing will, she was declared the heiress, and at the moment Nick has something to leave behind.
Poirot decides to announce the death of Nick. Shocked, Nick's friends buy flowers and wreaths for the funeral, and Hastings gets the fever. Meggie's mother sends Poirot a letter to her daughter, written by her immediately upon arrival at the Endhouse. One phrase in this letter makes Poirot take a fresh look at the case and unravel it.
The next day, Poirot gathers all the participants in the drama at the Endhouse. Among them are Charles Wise and Croft (she is in a wheelchair). Charles Wise announces to the audience that this morning received his will of his cousin, dated February, and has no reason to doubt its authenticity. According to the will, all the property of Nick goes to Mildred Croft in gratitude for the invaluable services she rendered to Philip Buckley, Nick's father, who once lived in Australia.
Suddenly, Poirot offers to arrange a spiritualistic session. Extinguish the lamp. Suddenly, in front of the eyes of those present, an unclear figure appears, as if floating in the air. Everything is in shock. A light comes on - in the middle of the room is a living Nick under a white blanket. Police Inspector Jepp appears, arresting Croft, a large forgery expert.
At this moment, someone shoots at Frederica, wounds her in the shoulder and receives a bullet from a policeman. This is her cocaine husband who has lost his human appearance. But he did not kill Maggie. Jepp, who had been on duty at the Endhouse since the beginning of the evening, had seen Nick take out a revolver from a secret niche, wipe it with a handkerchief and, going into the hallway, put it in Mrs. Rice’s pocket in her cloak.
Poirot claims that Nick killed Maggie to inherit the money of Michael Seton. Her name was also Magdala Buckley, and it was with her that the dead pilot was engaged. Police are already waiting for Nick in the hallway with an arrest warrant. Nick behaves arrogantly, does not deny his guilt, but before leaving he asks Frederica for an watch, which serves to transport and store cocaine. “For her, this is the best way out,” says Poirot. “This is better than the executioner's rope.”
