Armstrong examines the drink and finds it was poisoned, but since Marston poured it himself, the guests assume he committed suicide. Still, they find it hard to believe that such a high-spirited young man would want to take his own life. Marston’s body is carried to his bedroom and placed beneath a sheet. After a time, everyone goes upstairs to bed except for Rogers, who stays downstairs to clean up. As they enter their rooms, each guest locks his or her door. The house, so modern and gleaming, now seems horrifying in its blankness.

As he prepares for bed, Wargrave thinks about Edward Seton, the man whom the voice earlier accused him of sentencing to death. The defense defended Seton well, and the prosecution presented a poor case. Everyone assumed the jury would acquit Seton. Wargrave smiles, remembering how during his summing up “[h]e’d cooked Seton’s goose.” Downstairs, Rogers notices that although ten little Indian statues originally sat on the table, now there are only nine. Macarthur lies awake in bed, recalling how during World War I he discovered that his young wife was having an affair with one of his officers. Furious, he ordered the officer, Richmond, on an impossible mission, effectively sending him to his death. No one suspected him at the time, except perhaps one of the other officers, a man named Armitage. His wife became distant and died of pneumonia a few years later. Macarthur retired and lived by the sea, but after a time he began to worry, suspecting that Armitage had spread the story around and that people knew his secret. Now, lying in his bedroom listening to the sound of the sea, a strange feeling of peace comes over him, and he realizes that he does not really want to leave the island.

In her bedroom, Vera remembers her time as Cyril’s governess. She was in love with Cyril Hamilton’s cousin, Hugo, but Hugo was too poor to marry her and support both himself and her. Vera knew that if Cyril died, Hugo would inherit the family fortune. One day Cyril begged her again and again to be allowed to swim to a rock in the ocean. Vera pushes these recollections aside. As she passes the mantelpiece, she notices the similarity between Marston’s death and the first verse of the “Ten Little Indians” poem, which reads, “One choked his little self and then there were nine.”

Armstrong has a nightmare in which he stands at his operating table, realizing he must kill the patient on the table. The patient looks like Emily Brent, then like Marston. Rogers, worried because he cannot rouse his wife, comes into the room and wakes Armstrong. Armstrong rises and goes to find that Mrs. Rogers has died in her sleep, perhaps of an overdose of sleeping pills. Rogers says she took only the pills Armstrong gave her.

In the morning the guests rise, hoping to catch sight of the boat back to the mainland. Vera, Lombard, and Blore go to the summit of the island to watch for it, but it doesn’t appear. After breakfast, Armstrong announces Mrs. Rogers’s death to the group. The group is alarmed, and Macarthur gives Rogers his condolences when he returns to the room. When Rogers leaves the room, the group begins to speculate about the cause of his wife’s death. Emily Brent insists it was an act of God and that Mrs. Rogers died of a guilty conscience after hearing the recorded accusation of murder the previous night. Blore suggests that Rogers killed his wife in the hopes of covering up their secret.

After the meal, Blore and Lombard discuss their situation on the terrace and decide that the boat will not come. Macarthur, passing them, expresses his agreement in a dazed voice and wanders off, saying that none of them will ever leave the island. Meanwhile, a baffled and frightened Rogers shows Armstrong that only eight Indian figures remain on the table.

While And Then There Were None is a classic of detective fiction, it can also be seen as a forerunner of the modern horror or slasher story, with its almost supernatural overtones and the strange, serial killer–like murderer. And like a horror movie, the novel depends, both for suspense and for the working out of its plot, on foolish behavior by the killer’s victims. In these chapters, we see the guests repeatedly fail to grasp what should be obvious—namely, that Marston’s death could not have been a suicide and so must have been a murder. Because they refuse to admit this possibility, they are not on their guard, and the murderer easily disposes of Mrs. Rogers. Even once the characters realize what is going on, they continue to make obvious blunders, such as going places alone, that leave them vulnerable.

Part of this blundering seems to stem from a mistaken devotion to propriety and class distinctions. Even after his wife’s death, for instance, Rogers is still expected to serve as the butler and housekeeper, and he does so without objecting and without even showing much grief. The upper-class characters think nothing of discussing Rogers behind his back, with Blore going so far as to accuse him of murder. Eventually, Rogers’s devotion to his duties as a butler provides the murderer with an opportunity to finish him off.

During the night following Marston’s death, meanwhile, Christie uses her typical brief glimpses into characters’ minds to provide more information about their crimes. We learn the details of how Macarthur murdered his wife’s lover, for instance. At the same time, Macarthur is somewhat removed from suspicion, since his thoughts are manifestly not those of a murderer. Perhaps Christie exonerates him because he is about to die; indeed, his sudden, strange urge never to leave the island foreshadows his death the next morning. Meanwhile, Vera’s thoughts reveal how she went about disposing of her ward, Cyril, and why she did it, while Wargrave’s thoughts reveal only that he feels righteous about the execution of Edward Seton. Armstrong’s hallucinatory dream suggests rather heavy-handedly that he has a guilty conscience about the woman who died on his operating table. It also serves to plant suspicion in our minds: since Armstrong is dreaming about killing his fellow guests, perhaps he is planning to kill them for real.

A number of brief scenes in these chapters foreshadow later events. Just before Rogers brings him news of the missing figurine, for example, Armstrong emerges onto the terrace and tries to decide whether he wants to consult with Wargrave or with Lombard and Blore. He turns toward Wargrave, foreshadowing his later, foolish alliance with the judge. Also, the moment when Blore, Lombard, and Vera congregate at the summit of the island to await the boat foreshadows the end of the novel, when they are the only three left alive, and they again gather at the island’s summit. Meanwhile, the motif of the “Ten Little Indians” poem continues to be developed, with the disappearance of the figurines and the correspondence between the deaths and the verses of the rhyme. Again, it is Vera who notices the connection between the poem and the death of Marston, foreshadowing the effect that the verses later have on her fragile psyche.