June 1933. Independent, young Kitty Underhay has been left in charge of her family’s hotel, The Dolphin, on the tranquil English coast. But when several rooms are broken into and searched, including Kitty’s own, she quickly realizes that something out of the ordinary is afoot at the hotel. Soon, rumors are flying in the cozy town that someone is on the hunt for a stolen ruby. A ruby that Kitty’s mother may well have possessed when she herself went missing during the Great War.

Olive Belgrave needs a job. Despite her aristocratic upbringing, she’s penniless. Determined to support herself, she jumps at an unconventional job—looking into the background of her cousin’s fiancé, Alfred. Alfred burst into the world of London’s high society, but his answers to questions about his past are decidedly vague. Before Olive can gather more than the basics, a murder occurs at a posh party. Suddenly, every Bright Young Person in attendance is a suspect, and Olive must race to find the culprit because a sly murderer is determined to make sure Olive’s first case is her last.

London, 1923. Newly minted research assistant Saffron Everleigh is the first woman to hold the position at University College of London. When she attends a dinner party for the school, she expects to engage in conversations about the university's large expedition to the Amazon. What she doesn’t expect is for Mrs. Henry, one of the professors’ wives, to drop to the floor, poisoned by an unknown toxin. Dr. Maxwell, Saffron’s mentor, is the main suspect, and evidence quickly mounts.

A murdered opera singer. A duke drenched in her blood. For Bow Street Officer Hugh Marsden, the brutal killing is a straightforward case. Ever since his exile from polite society, the chance to arrest a high and mighty peer of the realm has never presented itself. Hugh won't snub the opportunity now. But Audrey Sinclair, the Duchess of Fournier, is certain her husband is wrongly accused, and she's determined to prove it to the arrogant Bow Street officer, even if she must employ her most peculiar ability—or perhaps curse—to guide her investigation. After all, a duchess can do as she pleases.

England. 1923. After a year away at finishing school where she learned etiquette, deportment, and the difference between a fish fork and a salad one, Kitty Worthington is eager to return home. But minutes after she and her brother Ned board the Golden Arrow, the unthinkable happens. A woman with a mysterious connection to her brother is poisoned, and the murderer can only be someone aboard the train. When Scotland Yard hones on Ned as the main suspect, Kitty sets out to investigate.