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.
Sherlock and Joan search for a murderer who used poisonous mushrooms to kill a botany professor and a group of the instructor’s students. Also, when Joan is disturbed by loud noise next door, she discovers her neighbor, Trent, is renting out his home through a vacation site that caters to hard partiers.
Holmes and Watson investigate a homicide in which the victim was murdered in a manner reminiscent of the crimes of an infamous, and already incarcerated, serial killer. Also, Sherlock and Joan tutor Detective Bell for a police sergeant’s exam that would lead to a promotion and a post at another precinct.
When Watson’s stepfather writes a crime novel based on her work with Holmes without her knowledge, an underlying issue in their relationship is revealed. Also, as Holmes and Watson investigate a retired FBI agent’s murder, they discover the man’s death is connected to an unsolved case from the victim’s career.
When Sherlock finds himself distracted by his father’s ongoing presence in New York City, he offers to help Morland resolve a work issue in exchange for his prompt departure home. Also, Holmes and Watson’s investigation into the double murder of two men who looked alike leads them into the world of facial recognition technology.
When Morland offers to use his influence to have Sherlock and Joan reinstated as consultants to the NYPD, Sherlock’s mistrust of his father makes him question his motivation to help. Also, with no work offers coming in, Watson wrangles a gig with the FBI investigating a triple homicide in a top secret research lab.
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.