On board a ship to England, a courier for the Royal Regent Museum is robbed of the Borgia Pearl by Naomi Drake. She hides the pearl in a camera and persuades a clergyman to carry the camera through customs. The clergyman is Holmes in disguise and he removes the pearl and takes it to the museum. When the pearl is displayed Holmes tests the security system and manages to disable it: while he does so, the pearl is stolen by Giles Conover, Drake's criminal partner. Conover is chased by museum staff, but manages to hide the pearl before he is captured. He is released shortly afterwards for lack of evidence. A number of related murders then follow, where the victims have their backs broken and their china and crockery smashed. Holmes establishes that the murders were committed by the Hoxton Creeper; Holmes and Watson examine the smashed crockery and discover that each victim owned a bust of Napoleon. Holmes visits the makers of the busts, near the museum, and realises that Conover hid the pearl in one of the busts before he was arrested. After getting a list of the owners of the busts, Holmes takes the place of the final owner and confronts Conover. Holmes tricks the Hoxton Creeper into killing Conover, before shooting the Creeper in self-defence.
