Sherlock takes on the case of a stolen artificial intelligence software program, but seeks out Joan when he'd rather disprove the computer's abilities than find the thief. Joan meets Sherlock head-on when she finds out he's met with Andrew without telling her.

When Watson joins forces with Holmes and Kitty to locate a missing nurse she used to work with, the woman’s trail leads them to another person who has recently disappeared.

Holmes and Watson investigate the murder of a professional skeptic, a man who debunked paranormal, religious and scientific phenomenon for a living. The case becomes urgent when his homicide reveals a potential threat to homeland security. Also, Captain Gregson’s daughter and fellow NYPD officer, Hannah, asks Watson for help with one of her cases.

A man takes hostages, including Joan, and threatens to execute them unless Holmes finds the person responsible for the death of his son. As Sherlock investigates, the captor gives him 16 hours to find the perpetrator before the statute of limitations on the crime runs out.

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.

Holmes and Watson enter the world of nuclear security when they investigate the murder of an ex-Yakuza gang member. Also, Captain Gregson is blindsided by a stunning personal confession from his daughter, Hannah, a police sergeant.

Holmes and Watson investigate multiple motives for murder when a zoologist is killed because of his numerous love affairs or his trailblazing research. Also, Holmes finds himself the victim of identity theft after his medical records are stolen.