At Mr. and Mrs. Unkerton's party in Greenway's House, Mr. Satterthwaite learns of a haunted window: No matter how many times it is replaced, it always contains the image of a gentleman in a plumed hat. When gunshots are heard, Satterthwaite finds that two of the guests have been shot dead, which is shortly followed by a sighting of the gentleman in the newly-replaced windowpane. Can Mr. Quin shed light on the mystery?

Lytcham Close, one of the oldest stately homes in England, is owned by the last remaining heir and ruled by his intolerable whims. Old Hubert demands complete silence when he plays music and times dinner exactly by a resounding gong. Rushing down at the sound of the second - or is it the first? - gong, Joan Ashby is about to find out that not only is dinner delayed, but something is going on that no one can explain. Everyone is thrown into disarray when Old Hubert never materializes and instead a new guest is announced: Hercule Poirot himself.

Waiting for his car to be fixed, Mr. Satterthwaite sits in a tea shop called the Harlequin cafe, thinking of his friend Harley Quin, whom he hasn’t seen in many years. Then, in a burst of sunshine, the very same Mr. Quin walks through the door, along with his diligent dog, Hermes. Satterthwaite is telling him the very long history of the family he is off to visit, when their conversation is interrupted by the abrupt entrance of a member of that very same family, intent upon replacing her harlequin cups.

Mr. Satterthwaite and Colonel Melrose are comfortably ensconced in the Colonel's study when the phone suddenly rings. Someone has been murdered, and, as the county chief constable, the Colonel lets Satterthwaite accompany him to the scene of the crime. The two of them have opposing opinions on why Sir James Dwighton has been bashed over the head with a blunt instrument. Rumor had it that red-haired beauty Laura Dwighton and her guest, the very attractive Mr. Paul Delangua, were engaged in an illicit affair, and Paul was thrown out by the disgruntled Sir James. But the facts of the murder all seem to add up too nicely....

Sane and sensible Edward Robinson secretly dreams of fast cars, adventurous women, and danger, but his fiancée, Maud, keeps him grounded in reality. When Edward wins money in a newspaper competition, he immediately buys the sleek red car of his dreams without telling Maud. Adventure swiftly ensues, as he is embroiled in high-society scandals that lead him to a significant transformation.

Throwing on an almost convincing French accent, Tommy is determined to act the Great Detective Hanaud to his and Tuppence's latest, lovely client. Miss Hargreaves has recently received a box of chocolates from nobody knows who, and, due to her dislike of chocolates, was the only one to not fall afoul of the arsenic-spiked treats. But, Miss Hargreaves is not the first recipient of such a gift; three other large country houses have received arsenic-laced chocolates. Miss Hargreaves is holding something back, and Tommy and Tuppence must take up residence at her house to discover the true culprit.

The recently married Alix Martin is obsessed with a recurring dream of her new husband's murder. Each time she can see the murderer clearly, and it's the mild-mannered man she had previously been engaged to, taking his revenge. But, what's worse is that at the end of the dream she thanks the murderer. Perplexed, Alix tries to calm herself by spending time in the garden of her picturesque cottage. But her gardener confuses her further by wishing her well on her trip to London - a trip which Alix knows nothing about. Now Alix is scared: Is the gardener imagining things, or is she?

Jane Cleveland is in desperate need of a job, and when she sees an ad for a woman of her description needed to impersonate a grand duchess, she cannot believe her luck. The royal retainers tell Jane that the job will be dangerous because attempts have been made on the Grand Duchess Pauline's life, but this only serves to make the job more appealing. Jane's disguise initially goes according to plan, but when she is kidnapped and drugged, it appears that her new employers are not all that they seem....

Major Hastings and Hercule Poirot are not interested in the mystery of the Spanish chest, which has been reported in the papers so often that it seems to be an entirely closed case. But, when Hastings persuades Poirot to attend a fabulous party given by Lady Chatterton, they discover someone sequestered upstairs who is desperate for their help. Will the contents of a dead man's pockets reveal to the inscrutable eye of Hercule Poirot who the culprit is?

An alarming telephone call, in which the phrases “it’s life and death” and “the table with the yellow irises” are whispered, causes Hercule Poirot to rush to the luxuriant restaurant Jardin des Cygnes, desperate to stop an impending murder and find the person behind the voice on the phone. After bumping into an old acquaintance, he is invited to join a dinner party in full swing. But, just as the dancing and champagne are overflowing, a morbid announcement is made and the lights go out.

A young banker is suspected of stealing one million dollars in Liberty Bonds on a transatlantic journey to New York, and appeals to Hercule Poirot to clear his name. Poirot learns the identities of the three people who hold keys to the locked trunk, but it won't be as easy to identify the true thief.

James has found himself at the fashionable resort Kimpton-on-Sea, all due to the persuasion of his girlfriend, Grace, who during the last few months of their courtship has become more difficult to deal with. Among the upper echelons of society, including the Rajah of Maraputna, James feels disgruntled and out of place. Eager to both irritate and win over Grace, James bypasses the queue to the changing rooms and ducks into the private huts on the beach so that he can be the first into the sea. It is only later that he realizes he has accidentally come into possession of a very valuable and sought-after object.

Maria Packington suspects her husband of having an affair. In an attempt to revitalise her marriage, she responds to an ad from Mr. Parker Pyne - who promises to provide solutions to unhappiness. Maria's life soon undergoes a rapid transformation....

Mr. Parker Pyne is having trouble trying to get to Beirut, what with his rusty linguistic skills and the less-than-comfortable traveling arrangements. But, with the help of a German pilot, Herr Schlagel, he is soon able to get his bearings. Herr Schlagel confesses that his thoughts are dominated by the mysterious and sudden death of one of his last passengers, who was in the company of Lady Esther from the House of Shiraz. Taking the initiative, Pyne writes to Lady Esther offering his services. When he arrives at the House of Shiraz, he waits to see what the infamously mad Lady Esther has to say for herself....

When civilian life proves too dull for Major Wilbrahams, he contacts Parker Pyne to escape his boredom. Pyne's assistant arranges a chance meeting with the beautiful Freda Clegg and the two join forces, but on leaving for Africa they encounter more than they had bargained for.