In the opening scene of Under Salt Marsh Episode 2, Eric engages in a conversation with Osian, who is staying at the pub with him. His stance against the creation of children is evident, and he expresses his disdain for their impact on the environment. However, despite his controversial views, Osian's alibi is solidified by multiple witnesses who can attest to his presence at the pub, leaving him in the clear.
The constant police presence in the small town is not well-received by the residents. They are more inclined to chalk up Cefin's death as a tragic accident and move on, particularly after what happened to Nessa. However, the evidence points to something more sinister.
The evidence includes an incomplete handprint, missing blue Wellington boots belonging to Cefin, and the presence of salt water in a freshwater area. The route from the sea to the ditch also aligns with the woods where Nessa was found dead. As more truths emerge, it becomes clear that Cefin and James were together after school but that James went home at 5pm, leaving a time gap of 5pm-7.30pm when Cefin was eventually killed.
Eric sends Jess to question James Rees, but Jackie is one step ahead. She arrives first with her drawings and decides to launch her own investigation. James confirms that the "beeman," Kieran Benbow, is the suspect. He is a reclusive beekeeper on Spider Island who has since retreated after being accused of being involved in Nessa's case. Jackie is now convinced that Kieran is involved and that it could be connected to Nessa's death.
When James's mother overhears the conversation and realizes that Jackie is questioning her son, she is incredulous and takes him away. James also refuses to speak to Jess. Meanwhile, Jackie heads over to see Kieran herself but finds Eric Bull already there. He tells her to back off, as she could be charged with breaking and entering.
Back on the mainland, Jackie visits Danny at the butcher's shop in town. He is still in shock, especially when he learns that Cefin's body was moved. Jackie also informs Danny about the beekeeper and how he apparently gave Cefin a present.
With each new piece of information, the mystery surrounding Cefin's death deepens, and the connection to Nessa's case becomes clearer. The investigation into Kieran Benbow intensifies, as Jackie and Eric race to uncover the truth before it's too late.
Returning to Eric Bull's narrative, he engages in a conversation with Jess, who brings up the Nessa case and his connections with both Osian and Kieran. There are clear implications that he's getting too close to this one, but Bull is determined to solve it before it's too late. He mentions a Romanian farmhand named August Antonov who could be a suspect. With no translator available and possible ties to both cases, he's definitely worth investigating.
That night, Jackie and Eric find themselves at odds when they arrive at the crime scene from opposite sides of town. She displays her knowledge, but Bull is annoyed at her interference and threatens to have her arrested if she continues. "You've got to investigate both cases, Bull," she says, as he storms back to the pub.
When Eric catches up with Jess that night, we learn exactly why Bull doesn't want both cases linked. Back then, Eric Bull accused Lydia, Nessa's mother, of killing her own child. This caused a deep rift between them and hurt Jackie deeply. Admitting now that the two cases are linked and the killer could still be out there throws all of this out the window – especially given it would mean a wrongful conviction for Lydia. Bull would need to confront his own demons and choices from the past, and that's not something he's willing to do right now.
In those days, Jackie was accused of gross misconduct at the station, which led to her departure. As for the evidence, the results came back on that stray hair. There's no match on the system, and the fingernails reveal no DNA either. It's theorized that whoever did this wore a protective suit of some kind. Cefin was held underwater, and he struggled. There are bruises on the back of his neck to confirm this, and the discoloration of his eyes appears to be highly linked to some sort of landfill or very acidic (or alkaline) concentration of water.
The thing is, the nearest landfill is actually 13 miles away on the mainland and it's way too far away to be linked. For now, all the townsfolk gather on the beach, including Kieran Benbow, to commemorate Cefin's life. Solomon gives an impassioned speech while Jackie uses this time to scan for faces and check the reactions. Solomon also tells the group that if they know anything, they should come to him instead of the police.
Things grow heated afterwards when Jackie confronts Kieran. Apparently, Kieran is actually Cefin's birth father, but before she can press him on the details, Danny heads off to confront him back at his place on Spider Island. He shows up with a shotgun, convinced that Kieran is responsible. Danny is hurt deeply that Kieran constantly played with Cefin and met him secretly in the woods to play without his knowledge. Danny sees himself as an imposter and starts to doubt himself as a father. He turns the gun on himself and starts crying. Just before firing though, Eric Bull shows up and snatches the shotgun. Tellingly, the camera pauses when Danny reaches down and touches the side of the sofa he's on. Could this be a subtle link to the handprint found in the mud?
It's here where Kieran reveals that the day Nessa died, Kieran was in the woods as well. However, he was with Cefin, playing. Back in town, Eric and Jackie finally talk and open up about the situation they're confronted with. Eric wants Jackie's help and has a hunch that Solomon and his farm could be a key piece they're missing. However, they do get a lucky break when Shelley arrives and informs them that there's a good deal of waste buried up at the old quarry. Eric brings Jackie along as they head over and see the rubbish for themselves. When they realize how far out of the way it is, they both have the same question: Why would Cefin go all the way there?
