When a body is found in a barrel, Holmes and Watson launch an investigation into the mafia’s ties to the murder. Meanwhile, Sherlock attempts to make amends with Detective Bell.

Business becomes personal for Sherlock when he is forced to partner with his estranged brother, Mycroft, to solve a case with life-or-death consequences.

When Holmes faces criminal charges in the aftermath of his recent violent behavior and relapse, his powerful father arrives in New York to fix his estranged son’s legal difficulties by any means necessary. Also, with Holmes and Watson’s consultancy with the NYPD in jeopardy, Holmes concentrates on the case of a missing wife believed to have been killed by her husband to try and get back in the department’s good graces.

A mysterious woman who organizes illegal, high-stakes poker games arrives on Holmes and Watson’s doorstep and tells them her life is in danger claiming to be a former associate of Mycroft, Sherlock’s brother. However, as the pair investigates, Joan becomes suspicious that their new client isn’t being truthful.

Joan and Kitty try to prove that a string of murders, stemming from an old case Sherlock and Kitty solved in London, is connected to an international government conspiracy with the Defense Intelligence Agency at its center. Also, Sherlock and Kitty’s relationship is strained after she shares life-changing news.

Tech billionaire Odin Reichenbach presents Sherlock and Joan with an extraordinary offer to help him with a program that can predict future crimes. Sherlock and Joan assist Bell when he tries to prevent a future crime of his own, as he races to locate a fellow NYPD officer planning a sniper shooting.

Tech billionaire Odin Reichenbach inadvertently provides Holmes and Watson with a lead that could give them evidence that brings him to justice.

Amidst Holmes and Watson’s battle with tech billionaire Odin Reichenbach, the investigators receive word of their old enemy and Sherlock’s former love, Jamie Moriarty.