One lonely night, a cabbie discovers that his intoxicated passenger has been suffocated with a handkerchief saturated in chloroform. The murderer, the victim, and the motive are all unknown.

Fergus Hume's first literary attempt became the best-selling mystery novel of the 19th century, exceeding even Sherlock Holmes. Hume was a law clerk in Australia, and thus the story takes place in the streets of Melbourne.