In Colchester a recently bereaved husband sees in a shop-window a plaster-cast made from a death mask of his dead wife. He is sure no death mask of her was ever taken; and in great distress, asks Gilbert Larose, the famous investigator, to solve the mystery. Larose is soon upon the track of a sinister figure, but immediately he finds the trail crossing that of a far greater criminal who believes he has committed two murders and will never be found out.
Larose relentlessly pursues him, but his quarry suddenly becomes aware that he is being followed. He strikes quickly and with a sure hand to save himself; yet, with his escape certain and his safety quite assured, he makes one great mistake. Larose then finds himself in danger from the authorities, and it is only by a master-stroke that he succeeds in extricating himself from a highly invidious predicament.