An ailing Poirot returns to Styles with Hastings nearly three decades after solving their first mystery there in order to prevent a serial killer from claiming more victims.
While in Belgium, Poirot relates to Chief Inspector Japp a case from his early days in the Belgian police force that nearly eluded the brilliance of his 'little grey cells.'
Poirot's pursuit of an infamous art thief leads him to a snowbound hotel in the Swiss Alps, where he is met with a plethora of mysteries and the reappearance of a familiar face from the past.
Poirot investigates the murder of a shady American businessman stabbed in his compartment on the Orient Express when it is blocked by a blizzard in Croatia.
A wealthy American heiress honeymooning on a Nile cruise ship is stalked by a former friend, whose boyfriend she had stolen before making him her new husband.
Poirot's rehabilitative health retreat on an island resort becomes an even more stimulating mental exercise when a flirtatious film star is found strangled on a nearby beach.
Elinor Carlisle seems to be the obvious murderer of her ailing aunt and the beautiful romantic rival who broke up her engagement, but Poirot uncovers darker motives.
The tyrannical patriarch of a dysfunctional but wealthy family summons his adult children for a Christmas reunion, but prior to the holiday his throat is slashed apparently by one of them.