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.