• The New York Times: ‘Smooth, highly original, and completely absorbing.’

15. Cards on the Table (1936)

‘The deduction,’ Agatha Christie writes in her Foreword to this volume, ‘must…be entirely psychological…because when all is said and done it is the mind of the murderer that is of supreme interest.’ There is probably no neater encapsulation of what makes Agatha Christie’s works so fresh, so fascinating, so many years after they were written. And this statement appropriately opens the novel that is regarded as Agatha Christie’s most singularly challenging mystery—it is, in fact, Hercule Poirot’s own favourite case.

Poirot is one of eight dinner guests of the flamboyant Mr Shaitana. The other invitees are Superintendent Battle of Scotland Yard (introduced in The Secret of Chimneys); Secret Service agent Colonel Race (who first appeared in The Man in the Brown Suit); Mrs Ariadne Oliver, a famous author of detective stories (introduced in Parker Pyne Investigates and who will figure in five more Poirots)—and four suspected murderers. After dinner, there will be a few rounds of bridge: the four investigators playing at one table; the four murder suspects at another. Mr Shaitana will sit by the fire and observe. This he does—until he is stabbed to death. The ultimate ‘closed-room murder mystery’ awaits the intrepid reader. Who is the murderer? And who will solve the crime?

Fair warning: Poirot casually reveals the solution to Murder on the Orient Express in Cards on the Table.

• Daily Mail: ‘The finest murder story of her career…Mrs Christie has never been more ingenious.’

16. Murder in the Mews (1937)

In the title work in this collection of novellas, Poirot and Inspector Japp collaborate on the investigation of a suspicious suicide. The supernatural is said to play in the disappearance of top secret military plans in The Incredible Theft—an incredible claim, indeed, as Poirot will prove. The bullet that kills Gervase Chevenix-Gore shatters a mirror in Dead Man’s Mirror—just the clue Poirot needs to solve the crime. And, while basking on white Mediterranean sands, Poirot stares trouble in the face—the beautiful face of Valentine Chantry, now celebrating her fifth marriage—in Triangle at Rhodes.

• Daily Mail: ‘All four tales are admirable entertainment…Mrs Christie’s solutions are unexpected and satisfying.’

17. Dumb Witness (1937)

Agatha Christie wrote this mystery for dog lovers. She was certainly one herself, dedicating the novel to her own pet. Captain Arthur Hastings, in his penultimate Poirot appearance (like Poirot, Curtain will be his last), again takes up narrative duties—along with, remarkably, the eponymous Bob, a wire-haired terrier who, upon careful inspection, declares Poirot ‘not really a doggy person.’ But Poirot is present to inquire into the natural-seeming death of Bob’s mistress, Miss Emily Arundell. Natural-seeming, except that Miss Emily had written Poirot of her suspicions that a member of her family was trying to kill her: a letter Poirot received too late—in fact, two months too late—to help. Poirot and Bob will sniff out the murderer nonetheless (and Bob will win a happy new home, with Captain Hastings who is, most decidedly, a ‘doggy person’).