Joan is the daughter of Mary Watson, and sister of Oren. Her stepfather had an affair, but her mother took him back. Her birth father fell out of the picture and her mother remarried a Mr. Watson. Joan was valedictorian of her class in medical school. When Joan was a surgical resident, she became romantically involved with Liam Danow, whom she had met when he was her patient. When he later started using drugs, Joan hosted an intervention and drove him to rehab. Although he was better when he came out, he started using drugs again after. Later, when she was a surgeon and accidentally killed a patient, she was suspended for two months. As she couldn't trust herself anymore as a surgeon, she let her license expire. After her relationship with Liam, she had learned a lot about how to deal with drug addicts, so when she decided to leave medicine, she decided to become a sober companion. She takes Sherlock Holmes on as a patient after his father hires her.