Sherlock requests he come along to a crime scene as his assistant.
John is introduced to Sherlock Holmes via an old friend from St. Mike is now an instructor at the hospital and, upon hearing John needs a new place to live, mentions another person saying the same thing that morning.
John worked at the Broomfield Hospital Chelmsford and the University College Hospital London. Bartholomew's Hospital as a British Army doctor and served as a Captain in the Fifth Northumberland Fusiliers.
John was deployed to Afghanistan, where he served for three years until being shot in the shoulder.
John Watson has a sister, Harriet Watson (nicknamed 'Harry'), whom he does not see often. John went to King Edward VI Grammar School in Chelmsford.
He studied medicine at King's College (London), where he also did his Bachelor of Medicine and Surgery in 2004.