"And Then There Were None" begins with ten strangers receiving mysterious invitations to Soldier Island, an isolated location off the coast of England. The guests include Justice Wargrave, a retired judge; Vera Claythorne, a former governess; Philip Lombard, a mercenary soldier; Dr. Armstrong, a physician; Emily Brent, a strict religious woman; General MacArthur, a retired military officer; Anthony Marston, a reckless playboy; Mr. Blore, a former detective; and Mr. and Mrs. Rogers, a married couple working as servants on the island.

Upon arrival, the guests realize that their mysterious host, U.N. Owen (a play on "Unknown"), is absent. During dinner, a recorded message accuses each of them of being responsible for a past crime. Shocked and unnerved, the guests attempt to rationalize the situation, but tensions rise as Anthony Marston suddenly dies after drinking poisoned whiskey. His death mirrors the first line of a macabre nursery rhyme framed in each guest’s room.

As the group grapples with Marston’s death, Mrs. Rogers is found dead the next morning, having apparently died in her sleep from poisoning. The guests realize that the deaths are following the structure of the poem, increasing their fear that the murderer is among them. When General MacArthur is found bludgeoned to death by the sea, the group fully accepts that they are being hunted one by one.

Paranoia spreads as they search the island, confirming there is no external threat—only one of them could be the killer. Mr. Rogers is next to die, struck with an axe while chopping firewood. Later, Emily Brent is found dead, injected with poison. Justice Wargrave takes charge of the investigation, but soon he is seemingly shot and presumed dead.

As the group shrinks, Vera, Lombard, and Armstrong form an uneasy alliance. However, Armstrong vanishes and is later found drowned. Suspicion intensifies between Vera and Lombard until Vera, believing Lombard to be the killer, shoots him in self-defense.

With only Vera remaining, she returns to the house and finds a noose prepared in her room. Overcome with guilt and psychological manipulation, she hangs herself, fulfilling the final line of the rhyme.

Later, police arrive on the island and find no survivors. The true culprit is revealed through a postscript confession written by Justice Wargrave. He orchestrated the murders as a form of justice against those who had escaped legal punishment. Faking his own death, he manipulated the sequence of events before ultimately taking his own life to complete the perfect crime.

"And Then There Were None" is a masterclass in psychological suspense, showcasing Agatha Christie's unparalleled ability to weave intricate plots and manipulate reader expectations. The novel remains one of the most celebrated works in the mystery genre.