Plot
Eight people arrive on a small, isolated island off the Devon coast, each having received an unexpected personal invitation. They are met by the butler and cook-housekeeper, Thomas and Ethel Rogers, who explain that their hosts, Ulick Norman Owen and Una Nancy Owen, have not yet arrived, though they have left instructions.
A framed copy of the old rhyme "Ten Little Niggers"[8] hangs in every guest's room, and on the dining room table sit ten figurines. After supper, a phonograph record is played; the recording accuses each visitor as well as the Rogers of having committed murder, then asks if any of the "prisoners at the bar" wishes to offer a defence.
The guests discover that none of them knows the Owens, and Mr Justice Wargrave suggests that the name "U N Owen" is a play on "Unknown." Marston finishes his drink and promptly dies of cyanide poisoning. Dr. Armstrong confirms that there was no cyanide in the other drinks and suggests that Marston must have dosed himself.
The next morning, Mrs Rogers is found dead in her bed, and by lunchtime, General MacArthur has also died from a heavy blow to the head. The guests realise that the nature of the deaths corresponds with the respective lines of the rhyme, and three of the figurines are found to be broken.
The guests suspect that U N Owen may be systematically murdering them and fruitlessly search the island. But as the island has no hiding places, and no one could have arrived or left, they are forced to conclude that one of the seven remaining persons must be the killer. The next morning, Rogers is found dead while chopping wood, and Emily Brent is found dead in the drawing room, having been injected with potassium cyanide.
After Wargrave suggests searching all the rooms, Lombard's gun is found to be missing. Vera Claythorne goes up to her room and screams when she finds seaweed hanging from the ceiling. Most of the remaining guests rush upstairs, and when they return, they find Wargrave still downstairs, crudely dressed in the attire of a judge with a gunshot wound to the forehead. Dr. Armstrong pronounces him dead.
That night, Lombard's gun is returned, and Blore sees someone leaving the house. Armstrong is absent from his room. Vera, Blore, and Lombard decide to stick together and leave the house. When Blore returns for food, he is killed by a marble clock shaped like a bear that was pushed from Vera's window sill. Vera and Lombard find Armstrong's body washed up on the beach, and each concludes the other must be responsible. Vera suggests moving the body from the shore as a mark of respect, but this is a pretext to acquire Lombard's gun. When Lombard lunges at her to get it back, she shoots him dead.
Vera returns to the house in a shaken, post-traumatic state. She finds a noose and chair arranged in her room and a powerful smell of the sea. Overcome by guilt, she hangs herself in accordance with the last line of the rhyme.
Scotland Yard officials arrive on the island to find nobody alive. They discover that the island's owner, a sleazy lawyer and drug trafficker called Isaac Morris, had arranged the invitations and ordered the recording. But he cannot be the killer, as he had died of a barbiturate overdose on the night the guests arrived. The police reconstruct the deaths with the help of the victims' diaries and a coroner's report and eliminate several suspects since, after each of their deaths, items had inexplicably been moved (for example, the chair on which Vera stood to hang herself had been set back upright). They also exclude Blore since suicide by falling clock seems highly unlikely. Ultimately, however, they are unable to identify the killer.
Much later, a trawler pulls up in its nets a bottle containing a written confession. In it, Mr Justice Wargrave recounts that all his life, he had had two contradictory impulses: a strong sense of justice and a savage bloodlust. He had satisfied both through his profession as a criminal judge, sentencing murderers to death following their trial. But after receiving a diagnosis of a terminal illness, he decided to put into effect a private scheme to deal with a group of people he considered to have escaped justice.
Before departing for the island, he had given Morris a lethal dose of barbiturates for his indigestion. His own 'death' on the island had initially been faked with the assistance of Dr. Armstrong under the pretext that it would help the group identify the killer. After killing the remaining guests, including Armstrong, he finally committed suicide in the same way, using the gun and some elastic to ensure that his true death matched the account of his faked death in the guests' diaries. Wargrave had written his confession and thrown it into the sea in a bottle in response to what he acknowledged to be his "pitiful human need" for recognition.