Endeavour: Series 4

Season overview

Role: Meticulous television and film archivist.
Task: Produce a JSON object for Endeavour Season 4.
Keys: overview (160-220 words), primer (array of exactly 4 concise bullet points).
Constraints: Use ONLY provided synopsis and sources. No invention, no guessing, no markdown, no asterisks, no headings, no bullet points (inside the string/text, though the JSON array provides the structure). Output valid JSON only.
Content constraints:
overview: Factual 160-220 word summary of the narrative arc.
primer: Exactly 4 concise bullet points summarizing essential previous lore, character positions, and stakes.
Synopsis: Series 4 takes place barely a fortnight after the series 3 finale. Endeavour is waiting for Sergeant's Exam results and self-medicating with whisky and Tännhauser to deal with heartache. Thursday and Win are dealing with grief; their home is empty because Sam has gone to the Army and Joan's whereabouts are unknown. The season explores 1960s pop, doctors and nurses, and the English pastoral.
Source [1]: Early days of young Endeavour Morse.
Source [2]: Third of the Inspector Morse series. Set from 1965 to 1972.
Source [3]: Endeavour Morse is a detective constable with the Oxford City Police.
Source [4]: Starring Shaun Evans, Roger Allam, James Bradshaw, Anton Lesser. Set from 1965 into the 1970s. Morse works alongside DI Fred Thursday.
Drafting Overview:
Set barely a fortnight after the events of the series three finale, the fourth series of Endeavour follows the characters as they navigate personal and professional recovery. Endeavour Morse, a detective constable with the Oxford City Police, is currently awaiting the results of his Sergeant's Exam. To cope with his heartache, he has turned to self-medication involving whisky and Tännhauser. Meanwhile, DI Fred Thursday and Win are processing their own sense of grief. Their household is notably empty, as Sam has departed for the Army and the whereabouts of Joan remain unknown. As the investigators continue their work in Oxford, the narrative expands into previously unexplored settings and themes. These include the world of 1960s pop, the lives of doctors and nurses, and an exploration of the English pastoral. The series continues to depict the early years of Morse, whose experiences as a detective constable will eventually shape his future. Through these various investigations, the characters must pick up the pieces of their lives while facing new