The Silver Death's-Heads, a gang of criminals who wear silver overalls and masks, have been committing seemingly random crimes for months. They become involved when they attack Paine L. Winthrop, a shipyard owner who has offices in the same building as Monk. When his office explodes, Monk and Ham investigate but are captured while reporting back to Doc Savage. With his other aides abroad, Doc Savage attempts to rescue them and solve the case alone. One of the first things he accomplishes is to deduce the nature of the explosion, which has eluded his aides and the police — it was caused by a three-inch shell.