The story begins with Hawkshaw, the great detective, smoking a stogy when the Colonel bursts into his room, excitedly informing him about the theft of the Queen’s necklace, valued at fifteen million shillings. Hawkshaw, having already read about the theft in the newspaper, feigns deducing the details of the robbery and impresses the Colonel with his apparent omniscience. The Colonel presents the only clue found at the crime scene: a cigar stub. Hawkshaw examines the stub and deduces that the thief is a tall, lanky man with large feet, cross-eyes, and a size 5 hat.

His reasoning is comically convoluted, attributing these characteristics to the shape and condition of the cigar stub. An old man wearing large green glasses, a stooped posture, white hair, and a long beard enters, claiming to have a clue about the robbery. He reports seeing a man, about five feet tall and three hundred pounds, jumping out of the palace window at the time of the theft. Hawkshaw then shares his theory of the crime, describing a tall, cross-eyed man returning from a fishing trip who used his fishing rod to hook the necklace through the open window.

Suddenly, Hawkshaw accuses the old man of being the thief in disguise. He leaps upon the old man, ripping off his beard and wig to reveal a tall, gangling man with huge feet and crossed-eyes. The thief attempts to resist arrest with a butter knife, but the Colonel subdues him with a howitzer, and Hawkshaw retrieves the stolen necklace from his pocket. The villain curses his luck as Hawkshaw handcuffs him, and the police are called to take him away.

Later, after collecting the reward for recovering the necklace, the Colonel asks Hawkshaw how he knew the man was the thief. Hawkshaw reveals that he smelled fish on the man's hands, indicating his recent fishing trip.