Professor Alistair Coke Norris packs up materials on the Booth Hill property development and leaves his office. A nervous young woman, Judy Vallens, is about to approach him when the Master of the College, Joylon Frobisher, tries to convince Coke Norris about something, but is rebuffed. A meeting of dons about Booth Hill begins. The next morning, Endeavour examines the scene of the deadly hit-and-run of a middle-aged man left curbside in a quiet neighborhood.
Endeavour identifies the body as Professor Coke Norris. Because the hit-and-run looks fishy – there's no debris, and his only wound is clean and to the head – Endeavour begins an investigation of his own. Coke Norris' wife, Millie, had just returned from their London flat, which they keep in order to visit their institutionalized daughter. In Coke Norris' office, Endeavour finds professor Ian Kern searching through his things, as well as a newspaper article about the Booth Hill property development. Millie reveals that Booth Hill was originally owned by Coke Norris' family, and was donated to Badeley College after the Great War to avoid payment of death duties. Coke Norris and Ian Kern were the only ones against the development, and he intended to speak against the deal the night that he died. Frobisher, who stood to make a significant amount of money from the deal, was in favor.
Dorothea sheds light on Booth Hill: tenant farmers are being forced off the land, and there are allegations of bribery of the council in the deal. The notorious London underground crime family, Sid and Gerald Fletcher, are said to be involved. Meanwhile, Endeavour and Thursday head to the Moonlight Room, a nightclub whose matches were found among Coke Norris' personal effects. There, Thursday encounters an old nemesis, Vic Kasper. Along with his thuggish son, Vince, Kasper owns the nightclub. There is an ugly history between the two and Thursday warns Endeavour to keep away. But written inside the matchbook is a phone number and the initials J.V. Mid-investigation, Endeavour is called home to visit his ailing father, a gambler who perceives his police officer son as a disappointment.
Thursday is convinced that the Kaspers are mixed up with Sid and Gerald Fletcher, while Endeavour pursues the matchbook to the home of Lady Mathilda's college student Judy Vallens and her roommate, Georgina. A cigarette girl at the Moonlight Room, Georgina had recently, suddenly, moved home. But when Georgina is found murdered, Endeavour learns from Judy Vallens that the girls were lovers, and Georgina used Judy's name and other pseudonyms in her work, which included prostitution. For a particular client whom she was to meet at a London flat, she'd been told to pick up a key from Frobisher's cubby at Badeley College. The client, town council employee Mark Carlisle, had bragged about the money he was going to make off the Booth Hill deal, but for the one professor who stood in their way. The girls contacted Coke Norris to warn him that they thought he was in danger. Oddly, the assignation took place in Coke Norris' London flat. Endeavour visits the flat and finds an envelope right inside the door. It contains a claim ticket, mailed from Coke Norris in Oxford to himself at his London flat the night he was killed. From the professor's cab receipts, Endeavour tracks him to the train station, where he'd gone in a cab the night of his death. There, he uses the ticket to claim a briefcase, finding within it a list of all the bribes and illegal transactions between the college and the council about Booth Hill.
Ian Kern reveals that Frobisher had once borrowed Coke Norris' London flat, then secretly had a key made, and lent it out to faculty and council members for their assignations. Armed with their secrets, he blackmailed them for their votes on Booth Hill. Meanwhile, Vince threatens Thursday's family and demands Coke Norris' Booth Hill papers. Endeavour boards a train to return to his sick father but turns up at the Moonlight, where Thursday, gun drawn, is in a standoff with Vince Vic, and their thugs. On the train, Endeavour had discovered in Coke Norris' papers connections between Vince and the Fletchers, and proof of checks bribing public officials, cashed by Mark Carlisle. Police take Vince and Frobisher into custody. Endeavour and Thursday return to speak to Millie.
Coke Norris' widow denies the allegations that Endeavour and Thursday lay out: That Millie used the car kept at their London flat to pick up her husband in Oxford, murder him, dump his body on the curb, and return to London. Why? Because she was obsessed with Ian Kern and imagined that he, who didn't stand to profit from the Booth Hill development, would marry her for the money she would make in the land sale. When she discovered that Judy Vallens had information that could derail the sale, she mistook Georgina for Judy and murdered her.
What then of Ian Kern? He's lying dead in the next room, a victim of Millie's insane ardor. As Endeavour calls an ambulance, she draws her gun again, but Thursday shoots her, saving the detective constable's life. Together, they drive to Endeavour's home, where he's by his father's bedside as the old man passes.