XYZ (1883) by

Sometimes in the course of his experience, a detective, while engaged in ferreting out the mystery of one crime, runs inadvertently upon the clue to another. But rarely has this been done in a manner more unexpected or with attendant circumstances of greater interest than in the instance I am now about to relate. For some time the penetration of certain Washington officials had been baffled by the clever devices of a gang of counterfeiters who had inundated the western portion of Massachusetts with spurious Treasury notes.