As the curtains lift on this episode of "Shetland," a gripping news bulletin captures our attention, revealing that a young Shetland schoolgirl has achieved a remarkable milestone by securing a coveted spot at Oxford University, making her one of the youngest to do so. Fifteen-year-old Annie Fleck, destined for greatness, will embark on her mathematical journey at the prestigious institution next year. In an exclusive interview with the news station, Annie shares her excitement.
Post the introductory segment, Cora McLean (played by Anne Kidd) attempts to engage DI Tosh McIntosh (Alison O’Donnell), who appears distractions. Cora elucidates that she was struck once in the chest, and 9mm cartridges were discovered at the scene. She suspects that Annie has been lying undetected for a full 24 hours. Tosh then seeks insights from DI Ruth Calder (Ashley Jensen), who fills her in on Anton Bergen. Ruth proposes questioning Malcolm Kidd to unravel his activities in Shetland. Earlier, Malcolm had confessed to Ruth that he shot his brother due to Bergen's involvement. They ponder whether Noah might have witnessed any part of the ordeal, with Ruth pointing out Noah's possible vantage point. Tosh remains convinced Noah saw something, evidenced by the bloodstains on his t-shirt. Ruth emphasizes the urgency of locating Ian. DC Sandy Wilson (Steven Robertson) confirms surveillance on Ian Bett's residence and workplace, promising to track his whereabouts the moment his phone is switched on.
Ruth tasks Sandy with gathering intelligence on Anton Bergen, a French national. Tosh directives Sandy to despatch a team to the Harris residence to keep them informed. Meanwhile, Lisa Friel (Tara Lee) and Angus Wallace (Jimmy Yuill) halt their strides, their gazes fixed on an unassuming building. Lisa dismisses it as just a structure, but Angus senses they're hiding in plain sight, cloaked in obscurity.
At the police station, Tosh and Ruth confront Noah's aunt and uncle, Michael (Andrew John Tait) and Noreen Stack (Lesley Hart). They delve into the harrowing incident, with Michael asserting Noah's physical well-being but acknowledging his mental trauma. They recount seeing Annie a couple of days prior and express their limited interactions with her and Noah since she left Ian. They profess ignorance about Ian's whereabouts and Noah's incoherent state. Tosh strives to communicate with Noah, whose utterances consist solely of numbers, repeated incessantly. Desperate for assistance, Tosh seeks help. In a private moment, Ruth gently informs Noah that he omitted 31, also a prime number, and reveals the heartbreaking truth about his deceased mother. She harbors hope that Noah might reveal what transpired, but he continues to claim amnesia, succumbing to panic.
Elsewhere, John Harris (Vincent Regan) and Fergus Harris (Macleod Stephen) receive a solemn visit from the police, who break the news to John. Back at the station, Ruth and Tosh brief everyone on Annie Bett, found deceased by her husband Ian the previous day. They also brief the team on Anton. Harry Lamont (Tibu Fortes) inquires about the murder weapon used.
Tosh asserts that the weapon in question was a 9mm semi-automatic, a rarity in the tranquil landscape of Shetland. Sgt. Billy Howden (Lewis Howden) inquiries about the elusive witness, prompting Ruth to confess that Noah is currently unhelpful. Their next step: locating Ian. Tosh reveals that Annie had something pressing to share with her, cut short abruptly by her untimely demise. Meanwhile, Angus keeps a vigilant eye on a van entering a nearby building, prompting Lisa to check on him. Distressed by his smoking habit, Lisa earnestly implores him to quit for her sake, confiscating his keys to embark on a quick shopping trip.
Tosh and Ruth engage in a conversation with Malcolm Kidd (Stuart Campbell) about Anton Bergen. Malcolm defends Anton, explaining that the incident wasn't entirely his fault. He confesses to playing poker with Anton at The Golden Dragon, where he lost a grand intended for his wedding with Eleanor. Embarrassed and ashamed, Malcolm chose to seek refuge at Andrew's house instead of facing Eleanor, which led to his unintentional discovery of Andrew and Eleanor's affair. He claims no further connection to Bergen beyond the poker game. As for Annie, Malcolm hasn't spoken to her in years.
Upon departing, Ruth and Tosh receive a startling update: Ian Bett's phone has been traced to the old mission. They hastily rush to the scene, desperate to find Ian. Tosh discovers Ian (Robert Jack) slumbering and rouses him, querying his whereabouts. Her keen eyes detect traces of blood on his shirt. In an interview room, they deliver the grim news to Ian, who firmly insists that no one ventured up to the lot where Annie was discovered, as work had been halted there. Tosh grills him about Anton Bergen, but Ian maintains ignorance. He evades questions regarding the bloodstains on his shirt. Ian reveals he attended Tara's party on Friday and suggests he may have headed to the mission afterward, despite evidence from the kids at the mission suggesting he didn't arrive until 5 am on Saturday. Ian's thoughts inevitably turn to Noah, and he expresses a desire to visit his son at the hospital.
Tosh and Ruth consult Harry Lamont about Ian's interview, who advises treating Ian Bett as a victim of a crime and releasing him. Billy is aware of JJ Huang (Nicholas Goh), who organizes the poker games. Sandy informs them that Anton arrived on the Isles six months ago and provides an address. PC Alex Grant (Conor McCarry) updates Sandy and Billy, revealing that Annie Bett had a heated exchange with a resident at Hem, where she volunteered on Friday afternoon – that resident was Lisa Friel. Billy mentions Lisa is with Campervan Angus. Tosh briefly speaks with Donnie Russell (Angus Miller), who doubts Ian's involvement. Post-call, Tosh hints at Ruth feeling conflicted, but Ruth denies any discord, insisting they weren't arguing.
They proceed to visit Karin Jakobson (Nathalie Merchant), who shares that she and her husband Stefan (Johannes Lassen) are renting the house. Anton, they learn, merely works for them. Stepping inside, they break the news to Stefan, who reveals that Anton was a nurse caring for their daughter.
Astrid, burdened by a genetic condition that compromises her respiratory system, sought solace in the tranquil haven of Shetland. Joined by her companions, she was overwhelmed with emotion upon hearing the news about Anton. Sandy approached JJ, who dismissed the incident as a mere friendly game, and relayed their findings. Meanwhile, Nathan Huang, played by Marlowe Chan-Reeves, returned with essential oil, inadvertently eavesdropping on Sandy and JJ's conversation about Anton and Annie. Karin revealed that she had last seen Anton on Thursday afternoon, expressing surprise at the notion of him being alone, as she had never witnessed him in the company of anyone.
Lisa's anxiety peaked when she spotted a police officer near the campervan, prompting her to swiftly conceal herself and make a daring escape in the vehicle. At the police station, the team convened to dissect the latest information. Ruth was startled to receive a call from someone within Organized Crime and Counter Terrorism, followed by a visit from Professor Euan Rossi, portrayed by Ian Hart. Through this encounter, Ruth learned of Annie's demise and Noah's survival, prompting her to exchange numbers with the professor for further discussions.
Billy then presented Ruth with incriminating texts from Ian Bett's phone, dated back to last week, which painted a dire picture for Annie. Tosh advocated for confronting Ian, and though Ruth volunteered to go alone, Tosh insisted on accompanying her. Outside, Tosh engaged with Tara Kirk, played by Nalini Chetty, and Joni Connal, portrayed by Gemma McElhinney. Once inside, Tosh placed Ian under arrest on suspicion of murder.
Elsewhere, John, Fergus, and Patrick Harris, played by Ross Anderson, deliberated on the police's evidence-gathering efforts. John appeared disoriented, leading Fergus and Patrick to prod him about the police visit and suggest a visit to Noah. However, John grew agitated and abruptly left the room, driving away in a huff.
During Ian's interrogation by Ruth, she grilled him about the hostile texts where he accused Annie of infidelity, to which he responded by explaining his frustration following their breakup. Ian's anger escalated when questioned about a threatening message where he vowed to kill "him" upon finding him, clarifying that he didn't know who Annie was seeing but sensed her growing secrecy. Regarding the altercation in the car park, Ian claimed Annie had berated him for showing up at the Harris residence unannounced. He couldn't recall his whereabouts after leaving the party, with the taxi driver later confirming he had dropped Ian off in Lerwick. Ruth pressed further, inquiring about Hayfield Lane, situated mere streets away from where Ian's taxi had deposited him. Ian, growing weary, declared his unwillingness to continue and shouted at Tosh, insisting it was over.
During a recess, Billy, Ruth, and Tosh analyzed Ian's statements when Sandy interrupted, revealing Anton had been making bi-weekly payments to the Harbour Hotel, with the last transaction occurring on Friday afternoon. Realizing Hayfield Lane was nearby, Sandy rushed to investigate. Just then, PC Alex Grant arrived, narrowly missing Lisa in his pursuit.
They speculate that Reverend Alan Calder (played by Steven Miller) might hold the key to Lisa's whereabouts, prompting Ruth to reach out to Alan, who confesses to having taken care of Lisa. In due course, Alan discloses to Ruth that Lisa and Angus have headed to Nesting. Lisa rejoins Angus, who is in need of updating their blog. She proposes a temporary relocation for a few weeks, an idea Angus hesitates to embrace at present.
Sandy informs Ruth and Tosh that Anton Bergen's boyfriend, Nathan, declined to visit the station. In their conversation with Nathan Huang, Ruth and Tosh ascertain that he and Anton had been meeting every alternate Friday, with Nathan sneaking back home before his father awoke. Anton had hinted at taking him back to Europe, but on the fateful Friday, their relationship took a turn for the worse. Nathan reveals that Anton received a phone call and, upon returning, broke up with him, citing a lack of love and urging Nathan to return home. Unfortunately, Nathan is unaware of who placed the call.
At the station, the team concurs that Anton's romantic involvement with Annie is unlikely. Sandy is tasked with uncovering the identity of the caller that night. Meanwhile, Ruth and Tosh encounter Cora, who has uncovered startling information—Annie had previously been shot, with bullet fragments still lodged in her shoulder, a detail conspicuously absent from her medical records. Outside, Ruth ponders the enigma that is Annie, and they decide to delve deeper into her past.
Fergus informs Patrick that he's unable to reach their father, and Patrick expresses his distaste for the woman residing in their house. Tosh receives a call from Billy, informing her that the blood found on Ian's shirt belongs to Ian himself, not Annie or Anton. Joni interrogates Tosh about Ian, insisting that he couldn't have killed Annie because they were together, estimating his departure around four. Joni confesses that Ian warned her to keep quiet but wonders if she'll be compelled to reveal the truth to Jamie. Tosh urges her to return home and implores Billy to take preemptive action before Ian's release.
As Ian is freed, John keeps him in his sights and deliberately strikes him with his car. Ian tumbles, his head smashing against the harsh concrete. Ruth receives a call from an OCCTU officer (played by John Scougall), who possesses pertinent information about Annie. She learns that the Chief Constable's Office had inquired about Annie, and she agrees to submit a report the following day. Professor Rossi approaches Ruth, revealing that OCCTU was already aware of Annie. Ruth realizes with a jolt that Annie was either one of their own or a spy, suspecting Professor Rossi might share a similar status. She seeks clarification on Annie's involvement, to which Rossi responds cryptically, hinting at something fatal that led to her demise.
