Warning: Major spoilers ahead

After discovering the quarry outside Solomon’s farm, Bull and the forensics team get to work. Deng questions how he was able to find it, but he doesn’t answer her, instead instructing her to make sure every inch of the wasteland is scoured for evidence. They need to know if Cefin was there at any point – and if there’s any presence of sodium hydroxide (the chemical found on Cefin’s body) from the leaking barrels.

As a new day begins in Morfa Halen, Jackie and Nisha teach their class about how to deal with a flood warning and evacuation, as well as skills that could help them, but Jackie is distracted.

After discovering a hair on Cefin’s body, Bull heads to the school to get a sample from his best mate James – with Jackie allowed to sit in the interview to calm him as his teacher with permission from Cara, James’s mum. Bull instructs her to stay quiet unless he asks for her input.

James is hesitant to talk, but Jackie helps him open up about Cefin, and he shares that Cefin was having nightmares that he wanted to go away. Jackie notes that she had tried to help him with them by telling him to face what it was he was afraid of. James reveals Cefin was afraid of ‘the black sow’ and James didn’t think it was real, Cefin had gone to find it, but refuses to share where he went to do so. Bull presses him on whether he went to Solomon’s farm, and James sheepishly nods in agreement.

A confused Bull asks Jackie what a pig has to do with a nightmare, and she shares that it’s an old Halloween myth in the area. It comes at night to hunt and capture the last child still out. She asks if there’s been any luck at the quarry, and he tells her not yet.

Splitting up their investigation, Jackie warns Bull to tread carefully with Cefin’s family, who won’t take well to being questioned. She aims to focus on the Bevan cousins who claimed to have seen Kieran Benbow in the woods the day Nessa went missing.

As the Hills have breakfast, they are visited by Jim the Chippy who warns there’s a boiled water order in place after the discovery of spilled chemicals at the quarry. Both deny having any knowledge of it, even though Shell was the one who informed Bull.

Bull and Deng arrive at the farm to speak to Solomon, Ned and Bryn. However, they are standoffish as they’re asked if they were working on Thursday. Solomon tells them both “there are no culprits here” discussing the wasteland behind the farm, and when Bull tells them they have reason to believe Cefin was at the farm before he died, he tells them they are misinformed because he never saw him.

Solomon scolds Bull for putting pressure on the family, but Bull encourages him to co-operate. Solomon stubbornly responds by demanding he be put in handcuffs if need be. The pair leave empty-handed but intend to know where everyone on the farm was that day, noticing that Ned is wearing heavy duty gloves.

As they leave, they’re approached by Ned, who asks when the wasteland situation will be cleared up. He then shares that Cefin could well have come and gone with no one the wiser, despite what Solomon said, because the farm is so big. When Deng asks about his farmhand August Antonov, he shares that he's not working that day. August was previously going to speak to the police regarding Nessa’s disappearance but changed his mind and stayed silent. They leave to find him.

The pair track August Antonov down the pub playing pool, but he claims he doesn’t speak English. Bull tries to apply pressure, but he makes a sharp exit when he realises Bryn Bevan has arrived.

Bryn announces to the pub that they’re doing everything they can to fix the waste in the quarry. When questioned about their part in its appearance by innkeeper Carys, he denies any knowledge of it. Before leaving, he takes a pointed jab at Bull by mentioning people “sticking their noses in and stirring up trouble”.

At the caravan site, Deng meets Victor Antonov and asks him questions about his cousin, August. Victor notes that his cousin ‘always has trouble around him’ but states he does not know what August was going to say regarding Nessa. He says August complains all the time about working at the farm for the Bevans, but from what he’s seen they’re good and generous people. They both send money back to their families in Romania, and while Victor struggles to get his enough, August’s family have received enough to fit a new kitchen.

Jackie heads to speak to Eddie Bevan – Ned's teenage son – who is messing around on a quad bike with a group of friends. She asks him about Nessa’s disappearance, and he snaps at her that she’s not a police officer anymore. When she tells him to cooperate or risk an officer taking him to the station, he buckles, but sticks to his story that he was playing in the woods with his cousin.

Jackie makes it clear she knows he’s lying, but Eddie tells her that she should be focusing on Cefin, not Nessa, and they’re not the bad guys she thinks they are.

Having no luck with Eddie, she heads to see Kath on the ferry boat. Kath tries to avoid her, but Jackie pushes her, reminding her she said Cefin’s death made her feel guilty. When she asks why, and if it was something to do with Nessa, Kath cracks and tells her that all six cousins, and Nessa, were actually playing on an old tractor near the quarry on the day she vanished. She admits they used to play pranks and dare Nessa to do things she didn’t want to do, which she realises now was cruel, but they were just kids. When Nessa threatened to tell her parents, the rest of the group threatened to hurt her, but she swears they didn’t – and then Nessa disappeared. She didn’t realise the impact until Cefin went missing.

Jackie insists she take her to the tractor by the quarry, which is still there after all these years. Kath apologises again to Jackie for lying, and for what she did to Nessa, but insists Cefin wasn’t at the farm the day he went missing. When Jackie shares that James told her he was, Kath warns her that kids lie.

As Jackie walks away, she passes a man from the environmental agency in an all-white Hazmat suit – and something dawns on her.

Heading to see Nisha, she shares Nessa and Cefin’s drawings and says while she initially thought it was a beekeeper outfit, it could actually be a hazmat suit. She asks if Nessa, Nisha’s niece, ever spoke about the quarry and the waste to her. Nisha says no and urges Jackie to stop trying to make Nessa and Cefin’s disappearance connect.

Jackie says, having found Cefin, she can’t let it go, but Nisha says given Jackie’s breakdown after Nessa’s disappearance, she needs to focus on her own wellbeing and not undo how far she’d come.

That evening, as the town turns in for the night, Jackie continues to root through a box of Nessa’s things, finding her old police report on the findings, and Solomon is seen at the farm by himself, weeping, with something clearly on his mind.

At the quarry, the investigation is still ongoing. Bull observes a news report warning of a severe storm heading their way.

At Gareth’s lodgings, two men in balaclavas break in while he’s sleeping. In a panic, he calls Bull, who is luckily only minutes away. Gareth observes the intruders leafing through papers. Seeing Bull’s car pull up, he confronts the men, who panic and injure him as they flee the house. Bull arrives and chases after them, but they both get away – though one leaves behind a trainer.

Bull tends to Gareth’s head wound and asks questions about what happened, noting they were looking for something, but have no idea what. Bull shares that one of Gareth’s measuring poles was found at the crime scene, hypothesising that perhaps some might think Gareth had something to do with Cefin’s death. Gareth is appalled by this and questions whether Bull truly believes that could even be conceivable. Bull evades that question, but worried the intruders might return, he takes him back to the hotel – much to the annoyance of Carys, who thinks they’ll be “getting up to hanky panky”. The pair head to separate rooms.

Bull is tending to his fungi examination and case recordings when he gets a knock at the door – Carys informs him that Jackie’s downstairs asking for him.

Updating him with everything she found, Bull thanks her but begs that she leave the detective work to him and take care of herself, accidentally letting on that he knows she is pregnant. She asks how he knows, and he says he could just tell from tiny details he’d observed over the past few days.

Jackie is surprised he’s paid that much attention, saying no one else has noticed – including the father of the baby, who doesn’t know. He reassures her as she admits doubting her ability as a mother but tells her to snap out of it because she didn’t fail Nessa or Cefin, and she won’t fail the baby. Before returning to bed, he encourages her to tell the dad and give him a chance to step up.

On his way back to his room, Bull notices Gareth has his TV turned up extremely loudly, to the point he can hear it outside. Knocking on the door, he checks in on him, before passionately kissing him. When Gareth asks him to look at him, Bull instead turns him around, and they sleep together.

Bull wakes up to a call from Deng, saying that something’s found at the quarry, and he rushes down there. Putting on a hazmat suit, he’s led to a body that’s been buried in a bag – though a red jumper poking out of it suggests it’s the long-missing Nessa.

He breaks the news to Jackie the next morning as she’s welcoming kids for school. While he notes they can’t definitely say – as she’d been lying in the quarry for three years – they were confident the body was Nessa. Jackie asks if he’d informed Lydia, her sister and Nessa’s mother, and if he’d apologised to her. He tells her they had just informed her.

Jackie, angered that Nessa was so close this entire time, storms off and leaves Bull to inform Nisha about the discovery.

Later that day, Bull heads to the ice-cream shop/makeshift police station, where Gareth approaches him, wanting to talk. Assuming it’s about the previous night, Bull blurts out that he doesn’t want to talk about a one-night stand. This is an awkward misreading, as Gareth is actually just giving him an update on the landfill. He notes the landfill must have been untouched for years, that the contaminates had come in through the soil – and most importantly, no sign of sodium hydroxide, which means Cefin wasn’t killed there. Gareth leaves Bull to cringe over the misunderstanding.

Sharing this information with Deng, she suggests pressing August Antonov, thinking he may be being paid for his silence. Bull finally acknowledges the Cefin and Nessa cases are likely connected and should be treated as such. Knowing he’s acting off, Deng asks if he’s doing OK - and he’s clearly not, with the investigations now weighing heavier on him than ever.

At The Ship Hotel, Jackie drinks heavily as she processes the discovery of Nessa’s body before drunkenly heading to Dylan’s house. She wakes him and initiates sex, but he stops when he realises how upset she is, and instead he comforts her as she breaks down in tears.

With hurricane force winds getting closer, Deng gets an email informing her of the results of the DNA test on the hair found on Cefin. While it didn’t belong to James, it did belong to a male relative of his – and the only one he has in Morfa Halen is his uncle, Dylan.

The next morning, Jackie is worse for wear and prays to the porcelain God in Dylan’s bathroom. Bull and Deng prepare to visit and question Dylan about the DNA match, but before they can leave, they’re stopped by an unexpected arrival – Solomon Bevan, who says he has a confession to make.