A storm of secrets and guilt broke over the islands in the penultimate episode of Shetland Season 10. DI Tosh McIntosh was forced to question everything she knew about her trusted friend Sergeant Billy McCabe, while DI Ruth Calder fought her own demons after a violent attack left her informant fighting for his life. With the murder of Eadie Tulloch still unsolved, a devastating confession in a windswept boat shed changed the entire course of the investigation.
The Tension Between Tosh and Billy Boils Over
The episode saw Tosh reach her breaking point. Armed with the knowledge of a suspicious £10,000 bank transfer from the late Robert Tulloch to Billy in 2001, she confronted her colleague. Billy claimed the money was simply a loan to help him and his wife Morag buy their first home, a story he stuck to with defensive anger.
However, for Tosh, the missing bank statement and Billy’s evasiveness were red flags. The normally steady detective was visibly shaken, her trust in a man she considered the “gold standard” of policing beginning to crumble. She ordered Billy to stay away from the station until she could clear the investigation, a move that left their professional relationship in tatters.
“If we find proof that Robert Tulloch was corrupt, we’ll have to report it… If he’s done anything illegal, then he’s finished,” Tosh later confided in Ruth, already fearing the consequences for Billy.
A Guilt-Ridden Ruth Calder Hunts for Justice
Parallel to Tosh’s crisis, Ruth Calder was consumed by a personal mission. Her young informant, Will Louden, was in a coma after a severe beating and an overdose. Knowing Will had been clean for months, Ruth was certain his condition was not self-inflicted but a targeted attack.
Her guilt over initially recruiting the vulnerable Will fueled a relentless pursuit. Her investigation led the team to Lewis Mitchell, the last person to call Will before the attack. DC Sandy Wilson eventually tracked Lewis down, finding him in possession of dr*gs, a large sum of cash, and Will’s phone. In custody, Lewis offered a name in exchange for leniency, claiming the local Callaghan family were the masterminds and that he worked for an accomplice on the islands.
Billy’s Shocking Confession at the Boatshed
The emotional core of the episode unfolded as a literal storm gathered over Shetland. Billy asked to meet Tosh at the Lunniswick boatshed, where the wreck of the fishing boat Lintie was stored. There, he finally told her the full truth about his past with Robert Tulloch.
Billy recounted the tragic storm from twenty years ago that claimed the lives of two local boys: Robert’s son Craig and Ally, the son of Arthur and Ellie Mair. While searching the washed-up Lintie for personal effects for the grieving families, Billy made a horrifying discovery.
“I found heroin on the boat instead, in fact ‘kilos of the bloody stuff,’” Billy confessed to a stunned Tosh.
Faced with a community already shattered by loss, Billy and Robert made a fateful decision. They chose not to report the dr*gs. Robert promised Billy he would dispose of them quietly. Billy now believes Robert betrayed that promise, likely selling the dr*gs and using the profits to fund a secret life, explaining the mysterious cash deposits into Eadie’s bank account. The £10,000 “loan” to Billy now looked less like help for a friend and more like a payoff for his silence.
For Tosh, the confession was a betrayal of the deepest kind. She was devastated not just by Billy’s poor judgment, but by the tragic ripple effect of that single decision.
“If you had reported it… Who knows how many lives could have been saved,” a tearful Tosh told him, thinking of the dr*g ring that now plagued the islands and victims like Will Louden.
A New Suspect Emerges as a Storm Rages
As the physical storm hit, the narrative twists converged. With roads closed, Ruth accepted an offer of shelter from Ed Tulloch, Eadie’s estranged son. Their professional relationship turned personal as they shared a bottle of rum while waiting out the weather.
This intimate moment was undercut by a chilling revelation. At the police station, the arrested Lewis Mitchell named his island contact: Ed Tulloch. The episode then cut back to Ruth’s home, where the camera focused on Ed’s handiwork—a running bowline knot he had used to secure her gate against the gale. This was the same distinctive knot used to strangle his mother, Eadie Tulloch.
This bombshell placed Ruth in unimaginable danger, suggesting she may have just spent the night with her murder suspect.
The Investigation’s Other Threads
Elsewhere in the episode, other suspects were eliminated or grew more complex. A fingerprint at Eadie’s house was matched to Tom Jameson, the father of pregnant teenager Jess. Under Tosh’s aggressive interrogation, Tom admitted he went to see Eadie to confront her about meddling in Jess’s decision to put the baby up for adoption. While he had motive and opportunity, he was eventually released.
The man who found Eadie’s body, Colin Waite, was also questioned. Ruth revealed a long-standing feud between Colin’s mother and Eadie, but Colin insisted they had moved past it and that Eadie had been kind to him after his mother’s death.
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The Stakes for the Finale
As the episode closed, every character was at a crossroads. Tosh must decide whether to report Billy’s past misconduct, a choice that could end his career and fracture their team. Ruth is potentially in grave danger, having gotten close to a man who may be a killer and a dr*g trafficker[ciction:2]. Sandy has a suspect in custody who has directly implicated Ed Tulloch.
All these threads—Eadie’s murder, the historic dr*g cover-up, and the current violent ring—are now tightly woven together, setting the stage for a tense finale.
The final episode of Shetland Season 10 airs on Wednesday, December 10, 2025, at 9 p.m. on BBC One and BBC iPlayer.
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