Blore readily agrees to help Armstrong and Lombard search the island for a murderer. Before they begin, Blore suggests that perhaps in stranding them all on the island and openly accusing each visitor of murder, Owen has indirectly brought about the deaths of Marston and Mrs. Rogers. But when Armstrong reminds Blore that this means Marston would have had to be carrying cyanide to kill himself, Blore rejects his own idea. When Blore questions how the poison could have gotten into Marston's drink, Lombard states that he believes Marston had several drinks and at one point in the evening had left his glass by an open window. When Blore suggests that one of them would have noticed someone tampering with Marston's drink, Lombard reminds him that they were all rather distracted by the mysterious voice and the accusations. Blore shifts the conversation's direction by noting how helpless they are to defend themselves. When he jokingly asks if anyone has a revolver, Lombard admits that he brought one with him.
The three men begin searching the island and find nothing unusual. Eventually, they work their way to the seashore, where they find Macarthur sitting alone, as if in a trance. Blore speaks to Macarthur, and the general remarks: "There is so little time'. Blore attempts to explain what they are doing, but Macarthur asks them to leave him alone. When Blore tells Lombard and Armstrong that he thinks Macarthur is crazy, Armstrong begins to wonder about the old man.
As the men complete their search of the island, Lombard notes that there are no boats at sea and remarks that a storm must be approaching. Blore suggests that they might light a bonfire to attract attention, but Lombard remarks that Owen probably anticipated this, telling the villagers to completely ignore anything unusual happening on the island. The group approaches a cliff, and Lombard feels they should investigate it by roping down: Blore heads off in search of a rope. Lombard notices Armstrong is deep in thought and asks what's on his mind; Armstrong replies that he's been wondering just how mad Macarthur really is.
Claythorne has some trouble interacting with Brent and Wargrave. As she looks at Brent, she envisions a young woman drowning, and as she looks at Wargrave, she envisions a young Edward Seton being sentenced to death. Claythorne walks to the seashore and encounters Macarthur, who seems as if he has been waiting for her. Macarthur remarks that it is a good place to "wait', and when Claythorne asks what he is waiting for, he replies: "the end". When Claythorne questions his comments, MacArthur states that none of them are going to leave the island, but what she can't understand, because she's too young, is that it's a tremendous relief. Again, Claythorne asserts that she doesn't understand and begins to fear him. MacArthur clarifies by talking of his wife, Leslie. He stresses how much he loved her and then admits he sent Arthur Richmond to his death. But doing so didn't completely solve his problem, since Leslie withdrew from him and eventually died, leaving him all alone. Macarthur suggests that she too will be glad "when the end comes". Claythorne rejects his comment, and the general returns his focus to the sea.
Blore returns with a rope, only to find Armstrong alone. Armstrong states that Lombard went off to test a theory, then remarks that Macarthur concerns him. He suggests that if they are looking for a madman, Macarthur seems to fit the profile. Blore counters that while Macarthur may be mad, he doesn't appear to be homicidal. Lombard returns, and they lower him down the cliff. Blore remarks that Lombard is an excellent climber, which prompts Armstrong to suggest that he must have done some mountaineering. When Lombard is out of sight, Blore remarks that there is something wrong with Lombard. Though he can't specifically identify what is wrong, he knows that he wouldn't trust Lombard, and openly wonders why Lombard would have brought a revolver to the island.
The men search the buildings surrounding the house to no avail. As they search the house, the notice Mr. Rogers on the terrace. They come upon a small staircase that leads to the Rogers' room. Blore suggests that there must be some space under the roof and remarks that it's the only place left for someone to hide. At that moment the men hear footsteps above them. Armstrong whispers that the sound is coming from the Rogers' room, and Blore suggests that this would be the perfect place to hide, since no one would suspect a murderer to be in the same room as the victim. They storm into the room, only to find Mr. Rogers, with a handful of clothes.
Blore apologizes to Rogers for bursting into the room. Rogers states that he was just moving some of his belongings to the guests' floor, provided they had no objections. When Rogers leaves the room, Armstrong pulls the sheet from Mrs. Rogers' face. He notes her peaceful look and wishes that he had his medical equipment in order to make some tests. As they leave the room to investigate the attic, Blore comments that Rogers moves rapidly and quietly. The men emerge on an upper landing, convinced that there is no one else on the island.
When Blore joins Armstrong and Lombard in their search for a murderer, the novel's first alliance is born. However, it is an imperfect alliance, as there is clear mistrust among the men. Lombard's recognition of the approaching storm again foreshadows the criminal and psychological storm that will soon sweep the island. His comment that the villagers were likely informed to ignore any unusual happenings on the island emphasizes the theme of isolation and reflects the complexity of the murderer's plot. Lombard's admission that he has a revolver will become troublesome as the guests' suspicion of each other grows.
Claythorne's consideration of Brent and Wargrave as potential murderers is a clear indication that the guests' opinions of each other are changing.
MacArthur's passive stance by the seaside reflects the years of guilt and unhappiness he has endured, as well as his desire to end his suffering. Mrs. Rogers' peaceful look at death illustrates MacArthur's belief that death can provide an end to one's suffering.