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. Meanwhile, Shinwell races to help the team, and Watson goes head to head with Moriarty.

Watson and the fellows spring back into action when Mary’s mother accidentally poisons herself while suffering from a rare form of dementia that is progressing with impossible speed. Meanwhile, Sherlock Holmes resurfaces after being presumed dead.

When a patient arrives at the Holmes Clinic plagued by a mysterious neurological disorder, Watson and the fellows discover they were forced to eat their parents amid a childhood survival incident. Meanwhile, Adam is struggling with how his future will change as a father.

Watson and the fellows race against time to save the life of Xavier, a 21-year-old athlete with a fast-growing, seemingly incurable cancer. Meanwhile, Mycroft Holmes lets Watson know his team’s work at UHOP may no longer have funding available.

In the wake of the car accident, Watson and Laila lie injured and awaiting rescue as the team races to find them before it’s too late. Meanwhile, in a state between life and death, Watson’s mind plays out a modern-day investigation of a case that has long haunted him.

Watson's father, Hamish, visits UHOP to introduce Watson and the fellows to his protégé, Annabelle, a saxophone prodigy with musically induced blackouts. As Annabelle's condition worsens, Watson must confront his long-standing tensions with his father in order to save her.

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. Meanwhile, Watson announces a new ambitious project that he has been working on.

Watson and the fellows race to save the life of a young woman who needs a lifesaving kidney donation. Meanwhile, Sherlock returns to help crack unsolved cases in Pittsburgh.

As Adam's wife goes in for a C-section to deliver triplets, chaos ensues when their OB-GYN passes out in the operating room. Meanwhile, a severe storm detours Watson and Mary's trip to find a renowned doctor to remove Watson's brain tumor.

Watson and the team work alongside Laila to help a patient named Maxine, a 30-year-old who looks 10 years old.

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.

Watson is sued for Wrongful Life by a long-term patient suffering from VACTERL association, after undergoing multiple painful surgeries.

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.

When Sasha discovers a link between her current patient, who has advanced cancers and distinctive lesions on his tongue indicative of Cowden syndrome, and a cadaver she dissected during medical school, the team traces the case to Amish country.

Watson and the fellows treat a comedian who collapses at an open mic night, but throughout the case her past is revealed to be much more complex than initially believed.

Watson and the fellows fight to revive a 30-year-old woman, Audrey, after her heart inexplicably stops repeatedly until they discover she has a rare phenomenon called Lazarus syndrome. As these revivals continue, she uses the short window of time available to right her greatest wrong.

Following his brain tumor diagnosis, Watson goes on medical leave to seek treatment, leaving Mary in charge of The Holmes Clinic as a notorious South American dictator demands Watson see to his mysterious autoimmune condition personally. Meanwhile, Ingrid grows more concerned about Beck’s obsession with Sasha.

Watson takes a major ethical risk when he decides to treat a sickle cell patient with an unorthodox surgery, and the team faces their own dilemma when they must decide whether to look the other way or help the young woman.

Watson runs into brilliant con artist and an old friend of Sherlock Holmes, Irene Adler, when her son Angus is admitted to UHOP for temporary paralysis. The fellows help Watson after he grows fond of Angus and pursue various leads to find a cure to his illness.

A microbiology researcher returns from an expedition to Siberia, leading to a possible outbreak of a revived pathogen. Watson reconnects with Sherlock Holmes.