In his narration, Dr. Watson notes that this is one of only two cases which he personally brought to the attention of Sherlock Holmes.
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, who dresses the stump where Mr. Hatherley’s thumb has been cut off, and then to Sherlock Holmes himself.
Hatherley had been visited in his office by a man who identified himself as Colonel Lysander Stark. He offered Hatherley a commission at a country house, to examine a hydraulic press used, as Stark explains, to compress fuller’s earth into bricks. Stark warned Hatherley to keep the job confidential, offering him 50 guineas (£52 10s, an enormous sum at the time, worth over 4000 GBP today.