Holmes and Watson travel to Paris to investigate the assassination of the French president. Disguising themselves as two Frenchmen, the duo journey overseas to the crime scene where they encounter a bizarre group of detectives and investigators. With their help, Holmes and Watson identify the culprits as dangerous anarchists whose ultimate goal is to outsmart each other and receive the biggest bonus from their leader, Monsieur Constantine.But as they draw closer to the inner circles of the faction, Holmes and Watson suddenly find themselves in mortal danger and forced to work for the enemy. They must use all their wit and deduction to escape the chains of the anarchists and bring them to justice. This includes Holmes being obliged to impersonate himself, and also to become a wanted criminal. Sherlock Holmes and the Boulevard Assassin will enthral all devotes of the Master and his faithful friend, Dr Watson.