A violent crime scene in a Parisian bar ignites a complex investigation that challenges conventional police procedure. Senior inspector Gévrol is quick to label the triple homicide a simple brawl, but his subordinate, Lecoq, suspects a deeper conspiracy involving hidden identities and aristocratic secrets. The apprehended suspect, claiming to be an acrobat named Mai, may in fact be the Duke of Sairmeuse, a man desperate to conceal his true lineage.

The novel is recognized for its intricate plotting and the introduction of the astute detective Lecoq, who would become a recurring character in Gaboriau's work. Critics have noted the author's skill in weaving a complex narrative that delves into the social strata of 19th-century Paris. The story's focus on deduction and the unmasking of secrets has been influential in the development of the detective fiction genre. While some may find the pacing deliberate, the detailed investigation and the exploration of character motivations provide a compelling read for enthusiasts of classic mysteries.