“It always starts with a body,” intones Superintendent Jolliphant (Kevin McNally) on the TV show Jolly For Short. Thursday looks remarkably unimpressed as the episode reveals a case of a crooked cop, but Win, beside him on the sofa, seems to be enjoying herself. Meanwhile, down at the station, CS Reginald Bright is distressed. “This is Oxford, not New York,” he laments. He’s upset about a sudden violent crime surge — the theft of Lady Mayoress’s car and an attack on a group of vagrants that has left one dead. DeBryn reports the victim was severely beaten, but the cause of death was a broken bottle to the neck. A partially burned £20 note lies in the debris on the floor nearby.
Sam: “My tin hat made me feel safe, but that wasn’t love.”
Still obsessed with the Blenheim Vale case in his spare time, Morse returns alone to the vagrants’ lair and discovers part of a white plastic mask. He meets one of the homeless people who tells him the attackers were “devils” in the shape of men “dressed like Fred Astaire.” The dead man was called Hughie, and his pockets included old, creased photographs of young children, a wedding ring, and a military beret from the Lancaster Rifles, Thursday’s old regiment. Thursday makes some calls and identifies the victim as Hugh Sellers, but there’s probably little chance of contacting his family.
The attack, which was shown at the top of the episode, revealed the attackers as The Debonairs, a group of aristocratic undergraduates inspired by A Clockwork Orange in their use of cosmetics, costumes (full white tie outfits), and love of violence, as well as masks and knuckle dusters. Archie Ormsby-Gore (Bill Skinner), the more timid member of the group, suggests they cool their activities down when the death of the vagrant is reported in the local newspaper. They sneer at him — who’d be interested in the death of an old tramp? — and tell him to move the car they stole to a more obscure location.
Morse is sent to check out a missing person report, artist Fred Baynard. His daughter Freya (Ayesha Antoine) thought he’d gone to the pub on his motorcycle, but he never came home. He’s a troubled man, but Morse says the police wait a week before investigating a missing adult. On his drive home, he finds a broken motorcycle headlight and a puddle of blood on the road. But he is too obsessed with reopening the Blenheim Vale case to follow up, despite the records being sealed, and neither Bright nor Thursday willing to pursue the matter. Morse found a report on Brenda Lewis, Landesman’s personal assistant who disappeared in 1963, but it’s yet another dead end.
Meanwhile, a dead police officer is found outside an abandoned factory. Thursday removes his hat as a mark of respect as he, Morse, and Strange join DeBryn at the crime scene. Other stations send men to help investigate, as Morse notices that the officer’s ID number on his collar is not a Thames Valley one, and he carries no ID, just a set of car keys. Morse searches the building and finds a packet of cigarettes and a condom wrapper, which may have nothing to do with the crime since it’s a popular spot for prostitutes. Lady Mayoress’ car is found nearby, with a library book beneath it by author Kent Finn, from the Superintendent Jolliphant series on which the TV show is based.
A librarian identifies it as one of six borrowed by David Astin (Michael Keene) at Mr. Cheeky’s Joke Shop. He's alive and well, suggesting his brother Raymond Swann, who currently stars as PC Constable Banks in Jolly For Short, which is filming around town, used his library card. David peels off his false mustache and drops his funny man act as he realizes the gravity of the situation, and Morse’s next stop is Raymond’s house. The keys from the corpse’s pocket open the car outside, where Morse finds a billfold with a ticket to the play Play Dead, and the remaining library books.
Morse and the team visit the Jolly For Short location. producer Michael Gatwood (Paul Bazely) says Raymond spent the previous day in a minibus driving between different locations. The cast interviews don’t go well since the actors want to talk about themselves, and no one knew Raymond well. Kenny, aka Superintendent Jolliphant, boasts about being in Play Dead, whereas Dicky, aka DI Chance (Leo Staar) is resentful that his role is being cut. Dicky smokes the brand of cigarettes as the ones at the murder site, but it’s not much to go on. The only event of any excitement that occurred on set recently was that a group of homeless people raided the catering and were driven off.
As the Debonairshit the town, this time in Napoleonic War–era uniforms, things are not going well in the Thursday household between the upcoming move and Sam’s behavior. Sam steals their money and spends it drinking beneath a war memorial in the local churchyard. They’re excited about Joan’s upcoming wedding to Strange. However, it's obvious they'd prefer Morse. Strange comes to dinner bringing his grandmother, but doesn’t know the house rules of no shop talk. Granny radiates disapproval even before Sam arrives home drunk and falls over noisily in the hall. Thursday, embarrassed at the scene, sends Strange back into the dining room when he offers to help.
Baynard’s body is found in the lake of a nearby aristocratic estate. According to DeBryn, he has suffered injuries consistent with a road crash. Morse finds yet another mask fragment, which fits the first one. He breaks the news to Freya, who takes him into the studio, explaining her father was manic depressive, but over the last decade, his personality changed. He was fearful of phone calls and late-night visitors; he was, Freya says, haunted. Baynard did the covers of Finn’s Jolly series, one featuring Blenheim Vale, along with a portrait of Brenda Lewis.
Morse is convinced Fred was leaving clues and was a member of the Downspout Drinking Club, to which Landesman and other key Blenheim Vale suspects belonged. But Thursday will not authorize an investigation of the Blenheim Vale grounds, despite Morse's certainty there's a body to be found. He breaks the news of his promotion and says he cannot risk the final years of his career. Morse has to risk his neck, even though Thursday wants justice for Hugh Sellers as much as Morse wants for Andrew Lewis. While Morse examines the Downspout Club records, he learns Ronnie Box already has been there; Box burns papers in his office before being disturbed by an armed intruder.
Joan finds Sam gloomily sorting through his old belongings and invites him out for a walk and a 99. They sit by a river, as Sam still won’t talk about his time in Northern Ireland. He is desperate to leave home, maybe for another country. He asks Joan about her engagement, and she gives this ringing endorsement of Strange: “He’ll never hurt me, and he makes me feel safe.” She knows she’s chosen the wrong man and phones Morse to invite him for a drink the next day.
The next morning Morse arrives at Blenheim Vale as does a backhoe he’s ordered. Work has barely started before Bright, Strange, and Thursday arrive, along with a couple of squad cars, sirens blaring. Morse fills Bright in on the clues in the paintings, but Bright has orders from above to close the excavation down; however, he will allow Morse to continue for the rest of the day. Bright has nothing to lose, with his retirement imminent, and he has not been able to forgive himself for the events at Blenheim Vale in Season 2 that left Thursday seriously wounded and Morse in jail.
Leaving the backhoe operator to work alone, Morse shows his colleagues the mask fragments, similar to masks sold in Mr. Cheeky’s Joke Shop. David remembers selling four to a young, posh man he guessed was a student. The same man returned to buy another mask and rent four Napoleonic War costumes. He returned the costumes in a terrible state –– torn, muddy, oily, and bloody. They were all cash transactions with no name given. But David found a Debonaires’ invitation in one of the pockets under the name of Ormsby-Gore. The Debonairs play croquet and laugh about the news of Fred’s murder. Nothing to do with them!
Morse and Thursday find the Debonaires enjoying a picnic and, a nod to Brideshead Revisited, with a teddy bear on the picnic blanket. There is some sniggering from the aristocrats as they show off their titles: Viscount Henley (Milo Mackenzie), Lord Freddy Alcaster (Jake Kenny-Byrne), and the Hon. Henry Brockhurst (Todd Bell). There is no such person as Mr. Ormsby-Gore — it’s Lord Archie Ormsby-Gore. Thursday invites them to the police station, and Henley takes offense, addressing him as “my good man.” Thursday responds, “I’m not your man, good or otherwise. I’m the Queen’s man, and I’m here to see her peace is kept.”
Morse asks Archie if his estate, where the Chief Constable shoots, is the one with a lake designed by Capability Brown and tells him the body of a motorcyclist was found there. Thursday signals to Strange and a group of uniformed officers to move in and arrest the young men. The Debonaires refuse to talk until their London lawyers arrive, but news arrives from Blenheim Vale — a skeleton has been uncovered. DeBryn identifies it as a male with a bullet wound to the head and shares the news that Fred Baynard was still alive when he was thrown into the lake.
Back at the station, the Debonaires insist Hugh Sellers was left alive and deny using a bottle to kill him. When Archie dropped off the stolen car, he saw “the man from the television” leaving the building. They admit to hitting Fred’s motorcycle, claiming his tail light was out. On his way to meet Joan, Morse is pulled over by two officers who insist on a breathalyzer test. Morse recognizes Stevens from before the Thames Valley merger, is not traffic police. Stevens hits him in the abdomen as a polite warning. Morse arrives at the pub long after Joan leaves. But Dorothea Frazil (Abigail Thaw) is there, having just interviewed actor Kenny Pryor. She tells Morse Pryor isn’t his real name; it’s Sellers.
Confronted, Kenny admits Hugh was his brother. When the vagrants invaded, they recognized each other. Kenny gave his brother £100, terrified the press would find out. He went to the vagrants’ basement after the Debonaires’ raid and found Hughie barely alive; killing him seemed the best solution. Raymond Swann saw them recognize each other and tried to blackmail him, so Kenny lured him to the derelict factory and pushed him out of the window. (Why would anyone agree to go to the top floor of a derelict building under the circumstances?)
Back at the site, a woman’s skeleton has been found, killed in the same execution style; the going theory is these are Landesman and Brenda Lewis. Bright is now fully committed to Morse’s cause; Morse, in turn, begs Thursday to send Strange away for his safety and the rest of the family. Ronnie Box phones Thursday to say he’s heading for South Africa; Bright must stop the investigation for everyone’s sake. That night, Peter Jakes (Jack Laskey), Morse’s one-time rival and one of the children abused at Blenheim Vale, arrives in Oxford. He left the country in Season 3 with his wife for a fresh start but has returned to join Morse in seeking justice.