New York, 1958. When Evelyn's mail is delivered during a luncheon in the Gold Room, she's surprised to find she has received a diamond tiara, which catches the attention of a costume jewelry sales team lunching nearby. Their leader, Lois Mitchel, is especially interested, but by the end of the lunch, Lois has choked and fallen into Evelyn's lap--and by the end of the day, she's dead.

The papers report on the death the next day, while also spreading news of a Gentleman Thief who's been leaving behind a red pocket square after robbing the city's wealthiest. Determined to figure out what happened to Lois, Evelyn devotes herself to the investigation.

The truth is as rare as a diamond and just as hard to crack, and Evelyn swiftly discovers that this particular mystery is multifaceted, too. From costume jewelry hawkers to wannabe Robin Hoods and a detective in residence at the Pinnacle, nothing is simple. But neither is Evelyn--and this case is hers to solve.