The story, set in 1889, mainly consists of a young London consultant hydraulic engineer, Mr. Victor Hatherley, recounting strange happenings of the night before, first to Dr. Watson. Upon arriving late at night at the appointed train station, Hatherley is met by Colonel Stark and is driven a considerable distance in a carriage with frosted glass windows to the house where he is to examine the machine. Hatherley is still under the spell of the 50 guineas and does not become afraid even when a woman at the house warns him to flee. He is presently shown the press and makes his recommendations as to needed repairs. Then, he rashly decides to inspect the press more closely. His discovery that its floor is covered by a crust of metallic deposit confirms his suspicion that the machine is not used for pressing fuller's earth. When he rashly confronts Stark with the knowledge, Stark tries to kill him. He narrowly escapes getting crushed to death when Stark turns the machine on, but he escapes the press with the aid of the woman. Pursued by the murderous Stark, Hatherley is forced to jump from a second story window, in the process getting his thumb severed by Stark's cleaver. Hatherley survives the fall but passes out in the rose-bushes, coming to hours later by a hedge near the rail station. Holmes then makes sense of the happenings, recognizing Stark and his allies as counterfeiters, but he, Watson, and the police arrive too late: the house is on fire, and the perpetrators have fled. The press was destroyed when Hatherley's lamp was crushed inside it, setting the machine on fire and ruining the criminals' operation, although they escaped with several bulky boxes presumably containing counterfeit coins. This case is one where Holmes fails to bring the villains to justice.