Captain Thomas "Tommy" Gregson is the captain of the 11th Precinct in the New York City Police Department, and a primary character in Elementary. He works alongside Detective Marcus Bell. He is Sherlock Holmes' police contact and supervisor. In "Pilot", he states that after the 9/11 attacks he was sent over to London to observe how the New Scotland Yard operate counter terrorism which is where he met Sherlock who was, at the time, working homicide.