An engineer, Victor Hatherley, attends Dr Watson's surgery after his thumb is chopped off, and recounts his tale to Watson and Holmes. Hatherley had been hired for 50 guineas to repair a machine he was told compressed Fuller's earth into bricks. Hatherley was told to keep the job confidential, and was transported to the job in a carriage with frosted glass, to keep the location secret. However, when they arrive, the house is on fire, and the criminals have escaped.