High-flying US cop Bill Hixon arrives in Boston to shake up the East Lincolnshire Constabulary, but when the coldest of cold cases turns up, it is Bill who finds himself shaken up.

Bill tries to reboot his authority by getting his team to focus on the difficult unsolved crimes, including that of the ‘Boston Bandit’ who was responsible for a series of post office robberies and a murder. Meanwhile, Bill’s professional relationship with Mary gets personal, Oleg pressures Muriel into betraying Bill, and Kelsey succeeds in getting Bill to finally engage with his dead wife’s memory.