The Crystal Stopper (Arsène Lupin, #5)

During a burglary at the home of Deputy Daubrecq a crime is committed, and two accomplices of Arsène Lupin are arrested by the police. One is guilty of the crime, the other innocent, but both will be sentenced to death. Lupin seeks to deliver the victim of a miscarriage of justice, but struggles against Deputy Daubrecq's ruthless blackmailer, who has hidden an incriminating document.