Thomas Watson left London two years ago and crossed the Atlantic to become a newspaper reporter in Philadelphia, 1920s Philadelphia, a city that rivals Al Capone's Chicago for its crime and corruption. Why would he go so far from family and friends? Admittedly, he was trying to get away - away from the shadow of his famous father, Dr. John Watson, and his father's even more famous friend, Sherlock Holmes.

Shortly after Thomas leaves London, Sherlock dies, and Dr. Watson takes on the responsibility of caring for Sherlock's older brother, Mycroft. After two short years in which Thomas finds little success in journalism, Dr. Watson dies suddenly; though Thomas stands to inherit his father's estate, he is also saddled with the responsibility of Mycroft, who has mysteriously shown up in Philadelphia, ready to move in. Puzzled by this strange turn of events, Thomas takes a walk and suddenly finds himself caught up in the biggest story of his career a suspicious explosion at a speakeasy, which kills the owner and his card-playing buddies.

The principal suspect of the police is Basil Meridan, a former British butler whom Thomas befriends and Mycroft hires as a servant. Needled into making a bet with a rival reporter that he can solve the mystery, Thomas is immediately hampered in his investigation by his editor, who fires him for spending too much time on a dead-end story. As he attempts to recover from this setback, he is escorted against his will to a meeting with bootlegger Boo Boo Hoff and his goons. They also want to know who the killer is, and provide their own unique encouragement for Thomas to find the solution to the mystery. All this makes it necessary to for him to solve the mystery, or lose his money, his job, maybe even his life. From the scanty clues that Thomas compiles, Mycroft is able to solve the mystery, but he is tight-lipped about the solution after all, Thomas should be able to figure it out himself! But can Thomas discover the murderer before he becomes his next victim?