The continuing stories of rookie Constable Morse. The young Endeavour Morse is on the case, before his signature red Jaguar, but with his deductive powers already running in high gear.

Last seen languishing in a prison cell and framed for a crime he didn't commit, Endeavour is compelled to return to duty when a young woman's baffling murder requires his singularly cerebral mind to solve.

As 1968 dawns, a year of change promises to disrupt the private and professional lives of Endeavour Morse and his colleagues. Endeavour's recent promotion leads him to reluctantly mentor new recruit Fancy, while Thursday is beginning to think about life after the police. But in Oxford, crime never sleeps, and the team continues to be challenged by mysterious and intriguing cases of murder, greed, and deception. Meanwhile, the rise of organized crime...

Endeavour and his colleagues are entering a new decade and era of change. Opening on New Year's Eve 1969, normal order has been resumed and the team reunited at Castle Gate CID, with Chief Superintendent Bright back in charge. However, the events of the past year have left their mark. Old friendships will be challenged, and new relationships will blossom.

Following the dramatic finale of Season three, Oxford's finest are picking up the pieces of their personal and professional lives. DC Endeavour Morse awaits the result of his Sergeant's Exam, while DI Fred Thursday and his wife Win struggle to cope with their children flying the nest. Sam gone to the Army and the traumatized Joan, gone off to who knows where? There are even greater challenges still to face.