The Adventure of the Engineer's Thumb

"The Adventure of the Engineer's Thumb", is the ninth of the twelve stories collected in The Adventures of Sherlock Holmes. A young London engineer, contracted to service a hydraulic press at a country house, discovers that the owner is using the machine for illegal purposes. After confronting the owner, the engineer narrowly escapes death and loses a thumb when the owner turns on him. Holmes deduces the actual use of the machine and sets off to bring the evildoers to justice.