Jeannie Hearne is spirited away in the middle of the night with no explanation. Her body is found the next day in the countryside, alerting the attention of the Oxford City Police. Endeavour may be suspended, but with the case being so close to his home, he begins an investigation of his own.

April 1967. As spring blooms, the death of artist Simon Hallward in a horrendous house-fire leaves Oxford City Police baffled as to the cause of the blaze. When a young housewife dies, seemingly of the same mysterious ’tummy bug’ that has seen half of Chief Superintendent Bright’s men go on Sick Leave, DC Endeavour Morse’s investigation leads him to an inner-city supermarket, Richardson’s, owned by a wealthy family of the same name, descended from a line of Quakers.

Early June 1967. A missing persons case - that of Danish au pair INGRID HJORT - proves far from routine, pulling ENDEAVOUR into the dueling worlds of Oxford scientific academia, the city's vast parks, Night School and the untamed wilderness of the Oxfordshire countryside.

Endeavour, recruited by his old college mentor Felix Lorimer to look into the safety of his estranged younger wife Nina, contemplates his police career as well as having to contend with unexpected strife in his personal life. Meanwhile, the murder of Cedric Clissold - a manager with a line in fashion - stirs up old gangland grudges as a notorious crime family appear to be in the frame as prime suspects.