Andrew Mittal was Joan Watson's boyfriend in Season 3. His sudden death led her to reappraise her life, and move back into the brownstone with Sherlock. Sherlock displayed considerable jealousy early in the Andrew-Joan relationship, but seemed to understand after some time that the other man was important to Watson as more than just a sexual partner. Sherlock did, however, continue to want the detective work to take precedence, something which Joan, as she contemplated a life with someone else, appeared less and less sure of.