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 cuddle. However, Bill's team are more interested in a mysterious amnesiac who has shot to local fame for playing the piano in the station.
Bill's soon reaping the plaudits when he succeeds in linking the stranger to the notorious cold case, only to realise the truth is more complicated that it first appears.
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

Bill battles a rising tide of fear when it seems a hugger is targeting Boston's pensioners, but he soon discovers there's much more to the case than meets the eye.

When the body of a young local man is found between two rival farms, a bitter feud is reignited. With the two families having been enemies for over 30 years, the team must deduce which of them is responsible. Bill and Muriel find themselves on opposite sides and both are determined to prove themselves correct. Bill wrestles with introducing Mary to Kelsey. Kelsey makes a new friend at the local school. Lydia resents doing Bill's dirty work as the redundancies commence.

Suspicion falls on members of the immigrant workforce after a suitcase containing the body of a farm owner is pulled from the river.

The discovery of a pyre of bodies puts Bill on the hunt for Frank McGill, a hitman notorious for his weapon of choice - a nail-gun. However, having been put into witness protection years earlier after turning in other members of the Maguire gang he worked for, Frank is now off-grid, so Bill sets his sights on tracking him down. Meanwhile, DS Blair is released on bail after information is leaked regarding the unlawful obtaining of key DNA, Commissioner Metcalfe discusses the financial benefits of selling off a disused training facility and the pressure mounts for Bill to resign.