This novel revolves around a plot to steal some goods secured safely within an impenetrable vault within the confines of Mr. Stoughton's business concern. Nobody seems to have any clue as to how the vault can be accessed, and yet access is gained once a day by person or persons unknown, by a means not known to anyone, apparently Mr. Stoughton himself included! Every clerk in the office is suspect, as the devious plot to plunder the vault's contents unfolds.