Warning: Major spoilers ahead

With the storm just hours away, water rising fast and Morfa Halen now cut off from the mainland, the community is in shock at the discovery of August’s body in the water outside The Ship Hotel. Who could be the killer?

With the town cut off by the storm waters, Deng, Jackie and Bull transport the body to the ice cream shop/investigation base, storing the body in one of the freezers. Dr Taman – the only doctor left in the area – comes in to inspect the body, but there’s nothing that immediately suggests what caused his death. While suicide is briefly considered, Bull, Deng and Jackie know that he was likely silenced - either for knowing about the waste still coming into Morfa, or for knowing something about Nessa’s death.

Either way they need to figure out who was paying him, what he knew, and where else the waste is being ditched. Fast. Time is of the essence as the storm comes in. Frustrated with her presence, Deng brusquely tells Jackie she should stay out of the investigation, but Bull is torn.

As Jackie heads home, she’s approached by Osian from the shadows. While he gives her a shock, he is just traumatised after finding August’s body. He says that he tried to warn people about the environmental catastrophe, but no one was listening. Jackie tells him his way of telling people – yelling at them and grabbing kids at school gates like he did with Cefin – doesn’t get anyone to listen.

Osian apologises, saying that he didn’t mean to scare the boy, and had tried to say sorry to him. She comforts him, knowing he truly meant no harm, and together, they walk back into town.

Overnight, the incoming hurricane can be seen approaching across the coast, and the residents head to higher ground. Gareth urges Carys, the Ship Hotel landlady, to go and take shelter with the Bevans. She refuses, wanting nothing to do with the family following the revelations of waste at the farm and the discovery of Nessa’s body. She, and most of the other townfolk, are heading to the forest instead.

Once alone, Bull tries to apologise for his aggressive behaviour towards Gareth the previous night but can’t quite verbalise his feelings. Gareth doesn’t accept it and tells him he needs to figure himself out.

Deng and Bull head to August’s caravan site – but someone has beaten them to it. By the time they arrive, they find August’s caravan ablaze – taking any evidence inside with it.

Waking from more dreams of Nessa, Jackie recalls something from her encounter with Osian. She finds him outside the chip shop and tells something he said didn’t match up to his previous statement. When did he try to apologise to Cefin? He told Bull that he’d gone straight home after the incident at the school and was at The Ship for the rest of the day. Osian admits he saw Cefin once more on the night he died but didn’t say anything as he feared he’d be suspected by the community. Jackie tells him that she can help him, but lying doesn’t help his case.

Osian admits following Cefin after school to try and apologise, but Cefin didn’t want to know - he and his friend ran off as soon as they saw him. Jackie figures out from his description he means James Rees, and they were on the salt marsh path not far from where Cefin’s body was found. Osian breaks down as he promises he did nothing wrong and apologises for not telling someone sooner. Jackie thanks him for his honesty and runs off.

As Jim the Chippy closes the doors to his business, water begins to flood the shop floor.

With 100 mile an hour winds coming ever closer, the entire town is deserted, and sewage water rises through the pipes in the shops begins to flood them.

At the caravans, Deng speaks to August’s cousin Victor, who says that there’s no way the fire was an accident as there was nothing in there that could cause such a blaze. Bull investigates what’s been left behind and notices the ground underneath the caravan’s entrance steps had just been freshly dug. Finding a buried bag, they look through it – discovering a journal and a series of letters detailing August’s efforts to let the council know about the waste in the quarry, and a map showing where Nessa was buried.

A CCTV camera set up near August’s caravan sees Ned Bevan banging on the door earlier that day. He receives no answer and leaves the scene. The footage then captures the arsonist, a masked man in a brown jacket. By his size alone, the Bull and Deng confirm it’s not Ned who started the fire, and unlikely to be any of the Bevans, but they still need to speak to him as he’s his biggest lead. Victor shares that before his death, August had become paranoid that someone was after him, hence why they installed the cameras.

Jackie joins the evacuees heading uphill into the forest, while the Bevans set up the farm to shelter those who need it. Shell notes no one will come to them because their name is tarnished, but Solomon is adamant that eventually people will come to their senses. The forest isn’t safe and he is ready to help his community just as in previous storms in years’ past.

At the forest, Gareth is also urging people to take shelter at the Bevans’, but no one is listening. Jackie spots Cara, who is struggling to get young James out of the car. She offers to look after him while Cara registers with the group’s organisers. Jackie uses the opportunity to ask James again about what happened the night Cefin died, assuring him he won’t get into trouble. She knows he’s lying about them going to the farm.

James admits he was on the path by the salt marsh but doesn’t want anyone to get in trouble. When she pushes him, she admits Dylan had told them not to go ‘because the Black Sow would get them’. Jackie tries to get more information, but James freaks out, jumps out of the car and into the arms of his horrified mum. Furious with Jackie’s pushing, both Cara and Nisha berate her, and Nisha reminds her that Nessa was her niece too.

With a new lead linking Dylan to Cefin’s whereabouts, Jackie demands to know where he is. Cara tells her he’s still in town, so she borrows a car to find him.

Deng and Bull split up – Deng looking for more information with August’s cousin, and Bull in search of Ned. The Bevans’ farm still has no evacuees present apart from the main family, and even Ned isn’t there. None of them share where he is, but Bull pleads with Solomon, saying there’s a concrete link between their landfill, Nessa’s death, and the fact Cefin was drowned in toxic water. As much as he doesn’t want to admit it, Solomon needs to realise this makes his family suspects, particularly Ned.

Bryn gets angry and lashes out at Shell, who confesses to being the one who told Bull about the landfill. Shell’s husband Danny then gets angry, saying he’s ashamed to be part of a family more concerned with protecting the farm than getting justice for the death of his son. That finally seems to get through to Solomon, who shares what Ned told him.

Ned and August were the ones to find Nessa’s body in the landfill – not him. She was already dead when they found her, but they buried her to protect the farm and family. Solomon tells Danny he understands how he feels, but in the same vein couldn’t stand there and let his son get in trouble.

But Solomon knows nothing about any money. He shares that after he was released from custody, he confronted Ned to ask if he had a part in any of this. No one has seen Ned since.

Jackie calls Bull to tell him what she found out from James but spots a distressed Eddie Bevan walking by himself in town. She asks him what’s wrong, and he tells her his dad, Ned, is planning to escape the town by boat, even as the storm bears down on him because he’s scared after what happened to August.

Bull overhears everything over the phone, and says he’ll go and find him. Jackie deduces he is volunteering to go as he believes Ned is somehow connected to the death of Nessa. Ignoring Bull’s pleas to stay away, she drives off to the quay.

At the ice cream shop, Victor looks over his cousin’s body, before telling Deng that he would like to take him home to Romania. He thanks Deng for listening to him, and she asks if he can help translate August’s notebook.

One note immediately catches his eye, and Victor tells her it didn’t belong to August, it belonged to him. It was a delivery notice to Sunnyside Amusement Park – where the sea wall building site is based, and Deng connects these are the regular deliveries of waste August had been telling her about.

Only three names are marked as signing off on these deliveries: Victor, Dylan, and once by Mac Jones. Realising what she’s found, she desperately tries to call Bull, who is too busy trying to call Jackie to answer.

At the quay, Jackie finds Ned preparing a boat and asks why he’s running. When she pushes him on what he did, he breaks down in tears, and she thinks it means he killed Nessa but he corrects her, saying she must have fallen in. However, he does confess to burying her.

Jackie is furious, asking how it’s not haunted him. He says it has, but now August is dead, he fears he could be next. As he rushes to get on a boat, Jackie chases after him, demanding more answers, even grabbing him. He shoves her off him, and she hits her head on a railing, knocking her out cold. By the time she comes to, Ned has set sail.

Bull arrives at the quay, but he’s too late to help Jackie or to stop Ned getting away. He angrily blames Jackie for Ned skipping out, and for getting involved once again despite his explicit instructions for her not to approach him. He yells at her for rushing in, saying she can never help herself, and that he’s sick of protecting her.

In the argument, Bull tells Jackie there’s DNA evidence linking her lover and father of her unborn baby, Dylan, to the murder of Cefin, and he has no alibi. He hadn’t told her before because she can’t handle things when they get personal, but she yells at him for accusing someone she loves, yet again. He calls her destructive and she storms off, with Deng arriving to see the last of their fight.

As the rain starts pouring down, Bull takes a breather in the car he borrowed from the Bevans, and Deng criticises him for going to Jackie instead of her, as she’s meant to be his partner in the investigation. She also judges him for holding back on pursuing Dylan as a suspect because of Jackie and doesn’t understand why he trusts her. When she threatens to report his behaviour, he flips, reminding her that they’re completely cut off from the world, there’s no one to report to right now, and that having only known him and Jackie for a week, there are things she couldn’t possibly understand.

When he asks why she tried to call him earlier, Deng shares about the waste coming in from truck deliveries meant for the sea wall – usually signed off by Dylan. However, something about the sea wall catches his attention.

As the rain continues to pour and the houses continue to be flooded, so is the ice cream shop – complete with all the evidence they had accumulated so far. Jackie arrives at Dylan’s house, eager to speak to him, while the entire community is still gathered together in the forest.

When Solomon realises no one is coming, he heads to the assembly point to plead with people to see sense and shelter at the farm. He understands everyone’s hesitance after the discovery at the landfill, but more lives will be lost if they continue to put themselves in danger. Slowly, they begin to fold, and the community begin to get in their cars to head to shelter.

But as people pack up to leave, Shell notices Cara in a panic – young James has gone missing.

As the weather worsens, Bull heads to the sea wall – which is beginning to crumble. He realises that the toxic waste has been hidden inside the concrete of the wall itself.

At Dylan’s house, Jackie waits for him to get home – and when he does, he’s wearing a white hazmat suit… just like the one from Cefin and Nessa’s drawings.