Sherlock and Joan investigate a case which involves a legendary pirate and his rumored treasure. All while the two struggle with their relationship with Shinwell.
Sherlock and Joan question how well they know Shinwell when they investigate the possibility he may have gotten away with the unsolved murder of his friend, a fellow gang member. Also, Sherlock and Joan's latest case puts them on the hunt for a treasure map rumored to lead to a fortune in pirate's gold hidden around New York City.