WesternJay McGraw has taken a leave of absence from Wells Fargo & Company to help out his friend Detective Fred Casey on the Chinatown police squad of San Francisco. Their mission to stern the flow of opium into the Bay City. Unable to crack the source of the opium, the squad calls in a visiting Londoner, Mr. Sherlock Holmes. Though Holmes does clarify some of the clues, he unwittingly plunges McGraw and Casey into grave danger . . .