Poirot and Race search all the guest rooms. Poirot wonders about the two bottles of nail polish in Linnet’s room. They find Pennington, Richetti and Rosalie all possess guns. The maid, Louise Bourget, is found dead under her bed.
Dr. Bessner examines the maid. She was stabbed with a sharp, thin weapon. Poirot notices a piece of torn money in her hand. Poirot believes she was struck while counting money. Poirot tells Jackie, Rosalie and Cornelia of the maid’s murder. Off to the side, Poirot asks Rosalie about her gun. Rosalie gets her bag, but finds no longer a gun inside.
Miss Bowers worries about getting Simon's worsening condition. Jackie is visibly upset about Simon. Poirot tells Race he knows the identity of the murderer. While Race and Poirot ask Simon about a misunderstood telegram, Miss Otterbourne enters and says she knows who killed Linnet. Mrs. Otterbourne saw a man go into the maid’s cabin. As she tells her story, BANG! Mrs. Otterbourne is shot with Pennington’s gun.
Pennington is shocked to hear of Mrs. Otterbourne's murder. Ferguson proposes to Cornelia but she isn't interested. Ferguson tells Miss Van Schuyler his intent to marry Cornelia. Miss Van Schuyler questions his social standing. Poirot tells Miss Van Schuyler that Ferguson is really Lord Dawlish.
Poirot questions Fanthorp and Pennington. Pennington says he wouldn’t gain anything from Linnet’s death, but Simon would. Simon is simple, easy to fool, trusting and admits his failures. Pennington admits that he dropped the boulder, but it was an accident.