Watson and the team are faced with an impossible choice when two lives hang in the balance, but they only have one vial of antidote available; Shinwell races to help the team; Watson goes head-to-head with Moriarty.

When part of the team falls ill after becoming targets of a sinister plot, it becomes an all-hands-on-deck situation to save them before it's too late; Watson announces a new ambitious project that he has been working on.

Watson confronts a traumatic event from his Army days that still weighs heavily on him after his friend's wife reaches out begging for help when her husband is seemingly having a psychotic break; Shinwell is asked for one last favor by Moriarty.

Watson is thrown into a detective case when he is unsure whether the patient he is treating for one of the most rare ailments in the world, alien hand syndrome, is guilty of pushing his brother in front of a bus to his death.

Ingrid's lies come back to haunt her when her sister Gigi needs to be treated by the team after she develops side effects to the secret treatments Ingrid put her through; Watson and Mary bond over a tragedy.

Watson runs into an old friend of Sherlock Holmes when her son Angus is admitted to UHOP for temporary paralysis; the fellows help Watson after he grows fond of Angus, pursuing various leads to find a cure to his illness.

While Watson and the team help a woman whose memory resets every three minutes, Watson struggles with auditory hallucinations and questions whether someone is behind his current decline; Moriarty plots his next move.

Stephens musters the courage to ask Watson to help him when his camgirl suddenly collapses during a video call; the team must act quickly to locate her before it's too late; Watson grapples with guilt over Sherlock's death.

Watson takes a major ethical risk when he decides to treat a sickle cell patient with an unorthodox surgery; Ingrid struggles to get her sister admitted to her spinal project.

When Sasha discovers a link between her current patient and a cadaver she dissected during medical school, the team traces the case to Amish country.

Watson and the fellows treat a comic who collapsed at an open mic night; the team becomes concerned when Watson collapses and suffers another traumatic brain injury.

Watson and the fellows investigate the perplexing case of a family man with a bullet lodged in his head who insists he is a Scottish soldier and seems to be hiding something nefarious; Watson looks for clues to whom his estranged wife Mary is dating.

Dr. John Watson resumes his medical career as the head of a clinic dedicated to treating rare disorders six months after the death of his friend and partner, Sherlock Holmes, at the hands of Moriarty.