Basil Rathbone in his classic Sherlock Holmes role. When the famous Borgia pearl is stolen from a courier aboard a channel ferry, the thief enlists the help of a clergyman to smuggle the gem through customs. Naturally, the clergyman turns out to be Sherlock Holmes (Rathbone) in disguise and he returns the pearl to its rightful owner. However, it is stolen again by the arch criminal Giles Conover (Miles Mander). Holmes must retrieve the pearl again but first he has to overcome Conover's associate, 'The Creeper'.