A steward comes to the smoking room and tells Poirot that Simon would like to meet with him. When Poirot arrives at Dr. Bessner’s cabin, where Simon is still recuperating, Simon asks Poirot if it would be okay for him to see Jacqueline. Poirot agrees to get her. When Poirot finds Jacqueline in the observation saloon, she’s surprised Simon wants to see her but agrees to come.
It’s expected that Jacqueline would want to see Simon, given how fixated on him she’s been and worried she was about him. But it is a little odd that Simon would want to see her, given that she shot Simon and may have been involved in Linnet’s murder. This hints that perhaps Simon is closer with Jacqueline than he’s let on.
Back in Dr. Bessner’s cabin, Jacqueline pleads to Simon that she didn’t kill Linnet and that she wants his forgiveness for shooting him the previous night. Simon reassures her that he’ll be okay. Poirot decides to leave them alone.
Again, the ease with which Simon believes Jacqueline and accepts her apology hints that the two of them are closer than they may have let on to Linnet and others on the ship.
Outside the cabin, Poirot sees Cornelia leaning over the rail. They talk about the weather, and Poirot remarks, “When the sun shines you cannot see the moon. But when the sun is gone—ah, when the sun is gone.” Cornelia doesn’t understand.
Poirot still has his mind on the case, as he recalls the sun and moon metaphor that both Simon and Jacqueline used earlier (to describe how Simon was too blinded by Linnet to pay attention to Jacqueline anymore).
As Poirot is walking, he hears fragments of an argument from inside a cabin. He knocks and asks for Rosalie, who appears. She is sulky but agrees to speak with him. They walk to the stern part of the deck where they’re alone. After talking a little, Poirot says bluntly that he knows Mrs. Otterbourne drinks heavily and in secret. He suggests that the previous evening Rosalie stole her mother’s alcohol and tossed it overboard. Rosalie admits he’s right.
Rosalie has been keeping a secret for the whole trip, and Poirot finally reveals that he knows about it. This is despite the fact that Mrs. Otterbourne lied to Poirot’s face earlier when she said she rarely drank anything alcoholic. With this information in the open, it seems that Rosalie’s suspicious activity isn’t related to the murder.
Rosalie explains that her mother, Mrs. Otterbourne, started drinking after her books stopped selling. Rosalie tried to stop her drinking, and her mother resented her for it. Poirot commends Rosalie for how she’s handled it so far and promises not to tell anyone. He asks Rosalie again if she saw anybody around at all when she was throwing the alcohol overboard. After a very long pause, Rosalie says no, she didn’t see anyone.
Mrs. Otterbourne was based on the real-life author Elinor Glyn. Given the fact that Agatha Christie makes Mrs. Otterbourne’s character an alcoholic with poor sales figures, it seems safe to assume that Christie wasn’t a fan of Glyn’s work. Just when it seems like the mystery of Rosalie has been cleared up, however, her pause before answering Poirot implies that she’s hiding something else—she likely saw something when she was throwing the alcohol overboard, but she won’t admit it to Poirot.