The three remaining guests sit eating breakfast in the kitchen. It is a sunny day. The storm has passed. Lombard suggests that they should try to signal the mainland for help using a mirror. But Lombard adds that although the weather is better the sea still hasn't gone down and there will be no way to get a boat to the island before tomorrow.
Christie has given the remaining characters a ray of hope—they only have to survive for about one more day.
Blore wonders what happened to Armstrong. He suggests that the doctor might have been thrown into the sea, but then wonders: by whom? Blore says he doesn't know but what he does know is that Lombard has the revolver, and maybe he has had the revolver for the whole time. Lombard says that this can't be because they all searched the house together and the revolver was replaced. But Blore still suspects him.
Blore is still preoccupied with the one known weapon on the island. Lombard's explanation seems reasonable, but reason doesn't matter anymore. No one can trust anyone else.
Blore says that the only fair thing to do now is lock up the revolver and both Lombard and Blore can hold a key. Vera says that they are both acting like idiots and have forgotten the rhyme. “Four little soldier boys going out to sea; A red herring swallowed one and then there were three.” She says that Armstrong is the red herring and isn't actually dead.
Lombard and Blore have become preoccupied with the details but Vera is still paying attention to the larger trends. She understands that Armstrong's disappearance is just a trick. Vera always seems one step ahead of everyone else.
But Blore says that they searched the island and Armstrong wasn't there. Vera brings up that they couldn't find the revolver before – everything has fit with the nursery rhyme so this must too.
Vera understands that you can't always trust your eyes on the island, but that everything will follow the rules that the murderer has set.
But, referencing the next verse, Blore says that there is no zoo on the island. But Vera says “Don't you see? We're the Zoo … Last night, we were hardly human anymore. We're the Zoo …”
Blore is too literal. Vera can see the subtleties – the three of them are barely human anymore. Like animals they are only trying to survive.
They spend the morning at the cliffs with a mirror and flashlight tying to signal the mainland. There's no indication anyone on the mainland noticed. They search the island again and see no sign of Armstrong. Vera says she feels safer outside and they agree to stay out of the house for a while, although Blore says they will have to go back in for the night. Vera says she can't bear it and Lombard tells her that she will be safe enough locked in her room.
The clean, modern house is more frightening than the natural landscape of the island. They know that they cannot control the house, and it holds secrets in spite of its orderly appearance. They feel more comfortable outside now that they have reverted to a more animalistic state. Society, with its rules and justice, is more threatening to them.
Vera feels almost happy in the sunlight. She feels like she can't die. Blore says he wants some lunch but Vera refuses to go back into the house. They argue a bit over who will get the revolver and then Blore gives up and goes to the house alone to get some food. Vera thinks that this is very risky but Lombard tells her that Armstrong is unarmed so it can't be too dangerous.
They feel that they know Armstrong is the murderer now, and that he has only hid himself, so with this knowledge Blore feels safe enough to venture off alone. He can avoid something that he knows exists.
Lombard starts to tell Vera that Blore's story about Armstrong and the footsteps clears both of them, but it doesn't clear Blore. He says that they should be careful of Blore; he might not even be an ex-policeman.
Lombard still doesn't trust Blore, but seems to trust Vera. He mentioned earlier that he cant imagine a woman committing such a crime, even though he knows that she has killed in the past. Though it's worth noting that Lombard has earlier stated that it is his imagination that will allow him to escape the island alive.
Lombard says that with his revolver he is going to take good care that Blore doesn't get them. He asks Vera why she trusts that he won't just shoot her and Vera says that she has to trust someone. But Vera still believes that Armstrong is the killer because she feels like someone is watching them.
Even when there are so few people left, they know that they cannot survive alone. They have to trust their unproven theories and animalistic instincts because these are the only tools they have. `
Vera says she once heard a story about two judges in a small American town that administered Absolute Justice, but in fact the judges didn't come from the natural world. Lombard responds that he doesn't believe in the supernatural. Lombard then asks if Vera actually did drown the kid. Vera denies it and Lombard doesn't believe her. He says that the whole thing probably involved a man. Vera admits that it did.
Vera believes that there is some supernatural power controlling this island. Lombard is far too practical to think such a thing. Vera still will not admit to her guilt, even though it seems obvious that everyone on the island committed some sort of crime. Vera is plagued by guilt but also doesn't quite believe it. She is in denial.
They both hear a thud and a cry and run back up to the house. Blore has been crushed by a great bock of white marble shaped like a bear – the one that was on the mantelpiece in Vera's room.
The bear that was referenced in the “zoo” nursery rhyme. Even this late in the game the murders are still perfectly planned.
Lombard says that Armstrong must be in the house and that he is going to go in and find him. But Vera stops Lombard and says that this is probably what Armstrong wants them to do.
They are now convinced that the murderer must be Armstrong because neither of them could have pushed the marble bear onto Blore.
Lombard decides that they should find a high place on the island and stay awake all night. They start walking and as they get by the sea they see a bundle in the rocks. They go closer and realize that it is Armstrong. He has drowned.
Lombard is trying to hold out until the sea calms tomorrow. Now that Armstrong it is only the two of them left on the island.