Bell jumped onto a trolley on busy Fulton Street and looked back. No one. He rode the trolley to the river, got off as if heading for the ferry, but suddenly reversed course and boarded the westbound trolley. He disembarked as quickly and swerved into Gold Street. He saw no one. But he still had an intense feeling that he was being stalked.

He entered a crowded oyster house and slipped a dollar to a waiter to let him out the kitchen door into an alley that led him to Platt Street. When he still saw no one following but still sensed it, he plunged deep into the ancient lanes of lower Manhattan—Pearl, Fletcher, Pine, and Nassau.

Try as he might, Bell saw no one following.

He was studying reflections in the showroom window of a manufacturer of assay and diamond scales, having just gone in the front and out the back of the Nassau Café, when he found himself on Maiden Lane—New York’s jewelers’ district. The upper floors of the four- and five-story cast-iron-fronted buildings that darkened the sky were a beehive of gem cutters, importers, jewelers, goldsmiths, and watchmakers. Below the factories and workrooms, retail jewelry shops lined the sidewalk, their windows gleaming like pirate chests.

As Bell cast a sharp eye up and down the narrow street, his stern visage softened and a quizzical smile began to tug at the corners of his mouth. Most of the men crowding the pavement were around his own age, smartly dressed in topcoats and derbies, but with shoulders sloped and faces bewildered as they blundered in and out of the jewelry shops. Bachelors about to propose marriage, Bell surmised, attempting to seal a momentous decision with the purchase of a valuable gem about which they feared they knew nothing.

Bell’s smile got bigger. This was a fine happenstance. Maybe no one had followed him after all. Maybe some “Higher Being” with a sense of humor had foxed his ordinarily trustworthy sixth sense to send him wandering into lower Manhattan for the express purpose of buying his beautiful fiancée an engagement ring.

Isaac Bell’s smile grew less sure as he joined the parade of men pacing the sidewalk and meditating upon the dozens of display windows that glittered with myriad possibilities and infinite choices. Finally, the tall detective took the bull by the horns. He squared his shoulders and strode into the shop that looked the most expensive.