Nellie St. Clair becomes distraught over the disappearance of Neville, her respectable, middle-class husband last seen in the second story window of a seedy waterfront dive and seeks out Holmes and Watson for help. When Holmes and the police arrive, they find a filthy beggar, not St. Clair, in the building which also serves as an opium den. The missing man's clothes are found in the room along with his son's broken toy and a bloody fingerprint on the window sill. Holmes initially suspects foul play especially after St. Clair's coat, weighted down with with copper coins, is found on a nearby riverbank. However, after the Great Detective interviews the beggar in his cell, he is able to solve the case and reunite Mrs. St. Clair with her husband.