The police call in Holmes and Watson to consult on a homicide "heard" by a cutting edge gunshot detection system when they can't find any tangible evidence that a crime was committed. Also, Sherlock and Joan become suspicious of Shinwell when he's the target of a drive-by shooting that reveals a connection between him and an unsolved murder.

Holmes and Watson investigate the murder of a man Sherlock considered one of New York's worst private investigators. Also, as Holmes stews over being beaten by Shinwell, he decides to take out his aggression by dismantling a local organization of private investigators.