The fourth series begins in the summer of 1967, barely a fortnight having passed since the events of the Series 3 finale, and we find Oxford's finest picking up the pieces of their lives, both personal and professional. Whilst Thursday and wife, Win, struggle to process the departure of both their daughter Joan and son, Sam, who has joined the army, Endeavour waits nervously to hear the result of his Sergeant's exam. Throwing himself into his work to mask the heartache of Joan leaving, Endeavour is quickly consumed by his duties with an array of new, perplexing cases landing on his desk.