Ralph Paton stands beside Ursula, smiling at Dr. Sheppard. Poirot points at Sheppard and says, “Have I not told you at least thirty-six times that it is useless to conceal things from Hercule Poirot?”
Poirot can be smug and arrogant at times—he has a high opinion of himself, and he gets pleasure from solving difficult cases.
Poirot reveals that he’d been suspicious of Dr. Sheppard ever since he learned that Sheppard visited Ralph on the night of the murder. Sheppard then decides to tell the truth. He says he went to see Ralph that afternoon, and Ralph told him about being in debt, and about his marriage to Ursula. After learning of the murder, Sheppard—recognizing that Ralph would be accused of the crime—urged Ralph to hide. Ralph agreed, thinking that Ursula might have killed Roger.
Poirot returns the reader’s attention to the fact that Dr. Sheppard visited Ralph Paton on the night of the murder—an event that, curiously, Dr. Sheppard tried to conceal. Sheppard claims that he did so because he wanted to protect Ralph from the police, and knew that he’d be the prime suspect in Roger’s murder.
Poirot explains that Dr. Sheppard hid Ralph in a nursing home for the mentally ill. Poirot tested his theory by inventing a fictional nephew with mental problems and mentioning him to Caroline, who immediately referred Poirot to hospitals where Sheppard had gone. At one of these, Poirot found that Sheppard had recently checked in a patient—who turned out to be Ralph. Ralph, Sheppard now realizes, was the “Home Office expert” Caroline saw. Ralph says that Sheppard has been loyal to him, but now sees that he should have come forward immediately.
In this chapter, many of the novel’s Chekhov’s guns come back into play; for example, Poirot’s nephew is revealed to be a stratagem by which Poirot learned where Ralph was hiding (with Caroline, yet again, providing the necessary information). We also once again see Poirot using unusual methods to trick people into divulging information they might otherwise want to keep secret.
Ralph now tells the guests what happened to him on the night of the murder. He left the summerhouse at 9:45, but has no alibi after that. He swears that he didn’t kill Roger Ackroyd. Raymond says that he believes Ralph, but adds that the police won’t. Poirot then announces why he’s brought everyone here tonight: he knows that the murderer is somewhere in the room. Tomorrow, he’ll tell Inspector Raglan what he knows, unless the real murderer confesses right away.
For a while, it seemed that Ralph’s version of events would solve the crime—either because Ralph was the killer or because he’d provide testimony that would implicate the real killer. Yet Ralph’s testimony doesn’t seem to add much to Poirot’s case. Poirot knows who the real killer is, though, and based on his behavior, it seems safe to conclude that it’s not Ralph.
Just then, Poirot’s Breton maid enters the room, carrying a telegram. Poirot reads the telegram and nods—now, he announces, he knows without a doubt who the murderer is. The telegram came from a “steamer now on her way to the United States.” Nobody speaks. Poirot repeats himself: the murderer must confess, or Poirot will send the truth to Inspector Raglan the next morning.
Strangely, Poirot is giving the murderer a chance to come clean in private, before he goes to the police. This might suggest that Poirot, unlike Inspector Raglan, isn’t strictly committed to obeying the law: he wants to achieve justice and learn the truth, but not necessarily by turning over the criminal to law enforcement.