The London and Scottish Bank is sending a huge shipment of Liberty Bonds to New York on the liner Queen Mary. Poirot, who suffers terribly from sea-sickness, is asked to see the bonds safely across the Atlantic.
Suggestions of a Communist conspiracy cast suspicion on a murdered woman's Russian servant. Meanwhile, Poirot has a rose named after him, and a ceremony at the Chelsea Flower Show makes him the centre of attention. Hastings receives a packet of seeds and develops hay fever.
Recovering from the horrors of World War I, British Army officer Arthur Hastings hopes to find peace and quiet at a country manor in the English countryside. But when the matriarch dies during the night from strychnine poisoning, Hastings enlists the help of an old friend staying nearby with other war refugees to help solve the murder: former Belgian police detective Hercule Poirot.
Marie Marvelle, a Belgian film star, receives threatening letters from a chinaman which demand her famous diamond, the Western Star. Marie visits her old friend Hercule Poirot in London, seeking his help, and Poirot tackles the case with relish.
Faced with an unreasonable amount of Spanish homework, Jeff's efforts to handle Señor Chang manage to help him, but not the rest of the class.
Under pressure to retaliate against China, General Naird wrestles with his conscience. Dr. Mallory makes an ominous threat, and Erin goes rogue.
Poirot is called in when the British Prime Minister and his secretary are kidnapped in France on their way to a League of Nations conference - and he is given just a day and a half to solve the case.
With the launch just days away, General Naird copes with an unprepared crew. Captain Ali searches for the perfect words, and Erin visits her mom.
It's conjugal visit time and General Naird is all systems go. Meanwhile, Dr. Chan and Captain Ali carpool, and Dr. Mallory deals with a time crunch.
A glamorous nightclub singer turned spy has stolen the US Navy's plans for a new submarine, and an FBI agent called Burt is in London to catch her. Burt dismisses Poirot as a gumshoe, and Poirot is likewise not impressed by the self-important G-man. Poirot is drawn into the case when it appears that the submarine plans will fall into the hands of the Fascist government in Italy unless they are recovered. When Poirot meets a young couple who've got an amazing bargain on a prime apartment, he sees a connection with the spy case.