21. Sad Cypress (1940)

Beautiful, young Elinor Carlisle stands serenely in the dock, accused of the murder of Mary Gerrard, her rival in love. The evidence is damning: only Elinor had the motive, the opportunity, and the means to administer the fatal poison. Inside the hostile courtroom, one man is all that stands between Elinor and the gallows—Hercule Poirot.

• Daily Mail: ‘Poirot solves another exciting case.’
• Charles Osborne, Agatha Christie’ biographer: ‘One of the most real, least schematic of crime novels. It is also unusual in that it employs the device of the possible miscarriage of justice…And it works superbly as a murder mystery.’

22. One, Two, Buckle My Shoe (1940)

‘Nineteen, twenty, my plate’s empty.’ But the reader’s plate is full indeed, as Hercule Poirot must follow a familiar nursery rhyme through a course of murder. The adventure is kicked off by the apparent suicide of a Harley Street dentist—who would also appear to have murdered one of his patients. Hercule Poirot has himself been this dentist’s patient on this very day, and suspects foul play. A shoe buckle holds the key to the mystery. But—five, six—will Poirot pick up sticks, and—seven, eight—lay them straight…before a murderer can strike again?

• The New York Times: ‘A swift course of unflagging suspense leads to complete surprise.’

23. Evil Under the Sun (1941)

‘There was that about her which made every other woman on the beach seem faded and insignificant. And with equal inevitability, the eye of every male present was drawn and riveted on her.’

Including Hercule Poirot’s. She is Arlena Stuart, the famous actress, enjoying—like the famous detective—a summer holiday on Smugglers’ Island, and she will become a common enough sight, sunbathing on the hot sands. Then one azure morning her beautiful bronzed body is discovered in an isolated cove, in the shade. She is dead, strangled. And Poirot, as luckless as ever when he attempts some down-time, will learn in the course of his investigation that nearly all the guests of this exclusive resort have some connection to Arlena. But who had the capacity and the motive to kill her?

Of note: The producers of Murder on the Orient Express and Death on the Nile released a film version of Evil Under the Sun in 1982; again, as in Nile, they cast Peter Ustinov as Poirot.

• Daily Telegraph: ‘Christie has never written anything better than Evil Under the Sun, which is detective story writing at its best.’
• Times Literary Supplement: ‘Christie springs her secret like a land mine.’
• Sunday Times: ‘Vivacious and entertaining.’

24. Five Little Pigs (1943)

A staggering bestseller upon its publication—running through 20,000 copies of its first edition—Five Little Pigs (published in the U.S. as Murder in Retrospect) concerns a murder committed sixteen years earlier. Carla Crale prevails upon Hercule Poirot to investigate the crime that sent her mother, Caroline, to prison for life (where she died). Caroline had been found guilty of poisoning her estranged husband, Carla’s father, Amyas Crale, the famous artist. Poirot’s investigation centers upon five suspects, still living, whom he convinces to speak to him and to record their own memories of the long-ago incident.