Dr. Armstrong rushes to Marston and, in disbelief, pronounces him dead. Macarthur asks how Marston could have died from a slight choking spell, and Armstrong notes that it was actually asphyxiation. Armstrong sniffs Marston's glass and notes that his death wasn't by natural cause. Claythorne asks if something was in Marston's whiskey, and Armstrong affirms her point, suggesting that it was likely cyanide. Armstrong then tastes both the whiskey and the soda water and states that neither is tainted. Lombard questions whether that means Marston put the poison in his own drink; Armstrong suggests that it appears so. The group debates the likelihood of Marston committing suicide and eventually agrees that this has to be the most logical answer.
Armstrong and Lombard carry Marston's body to Marston's room and cover the body with a sheet. When they return, Brent suggests that they should all go to bed. They agree, and Rogers states that he will retire as soon as he has cleaned up. As each guest goes to his or her room and locks the door.
In his room Wargrave rethinks the details of the Seton trial, noting how the defense had performed masterfully but the prosecution had bungled the case. With some pride, he recalls how he had been able to sway the jury and get the conviction.
As Rogers is cleaning up, he notices that one of the Indian figurines is missing.
Alone in his room, Macarthur remembers the events surrounding Richmond's death. He recalls how he had discovered that his wife was having and affair with Richmond and how he had purposely sent Richmond on the mission which took his life. He wonders how anyone could have uncovered the truth and recalls that a young soldier named Armitage may have suspected. Perhaps Armitage told someone about the event. He notes how although his wife never learned of the incident, when he returned from the war their relationship was never the same. She died of natural causes several years after his return. Following her death, he moved to Devon and found it to be a pleasant enough place; however, after a time, he sensed that the locals were talking about him behind his back. As a result, he became very reclusive. He wonders if the other guests suspected the truth, and he notes that Claythorne and Brent couldn't possibly be guilty of their charges. He realizes that he doesn't really want to leave the island, returning to his troubles at home.
Claythorne lies in her bed thinking about Hugo and the events surrounding Cyril's death. She recalls how she would sneak out for romantic walks with Hugo. She had proclaimed her love for him, but immediately after Cyril's death, Hugo had disappeared. She notes how Hugo claimed he couldn't marry her because he hadn't any real money. Of course, he would have received a substantial inheritance if Cyril hadn't been born. She remembers how Cyril was a rather weak child. As she takes several aspirin, she wishes she had brought something stronger and then notes that if she were going to kill herself it would be with an overdose of pills, not cyanide. As she passes the mantle, she notes the first line of the poem: "Ten little Indian boys went out to dine; One choked his little self and then there were nine". With some horror, she realizes how the line reflects recent events. She knows she doesn't want to die, and asserts that death is for other people, not her.
Marston's death suggests just how easily murder can be accomplished, a point the remainder of the story illustrates. The initial assessment of Marston's death as a suicide introduces the notion of misinterpretation of facts; it also hints at the power of self-delusion, for none of the guests wants to believe that Marston may have been murdered.
Wargrave's admission to himself that he swayed the jury in the Seton case and MacArthur's recollection of the events surrounding the death of Richmond further illustrate the theme of public deception. Yet MacArthur's notion that Armitage may have shared his suspicion of the true cause of Richmond's death demonstrates how difficult it is to fully conceal a secret.
Macarthur's assertion that he doesn't want to return home is the first indication that concealing a secret can exact a high price on the concealer. Of course, Claythorne's feeling that she doesn't want to die serves as a clear counterpoint.
The fact that each guest locks the bedroom door when he or she retires demonstrates that the guests are becoming fearful and are perhaps beginning to deeply mistrust one another.
Claythorne's reflection on overdose, a possible form of suicide, foreshadows her eventual death.