Following the death of Oxford crime boss Harry Rose, a power vacuum triggers a violent struggle between rival gangs, specifically the Matthews brothers, for control of the underworld.
Already dealing with declining health (a bullet still lodged in his lung) and a suspension for attacking an informant, Thursday is pushed to his breaking point when he realizes his daughter is in mortal peril.
Morse is approached by his former Oxford tutor, Dr. Felix Lorimer, to investigate Paul Marlock, a man involved with Lorimer's estranged wife, Nina. Morse soon discovers that Marlock is also secretly seeing Joan Thursday.