In the fourth episode of "Under Salt Marsh," the story unfolds with Solomon's arrival at Jess and Bull's doorstep. It's a poignant moment as we flash back three years, revealing how Solomon was first informed that a massive amount of waste was being dumped on his land—specifically, in the quarry where he found Nessa's body, badly burned. He had wrapped her in tarpaulin and kept the grim discovery a secret to protect his family and their farm. However, Bull is relentless in his pursuit of answers, probing Solomon about Nessa's disappearance and his potential involvement in her demise.
The mystery deepens when we learn that Solomon doesn't reveal who first informed him about the waste. Could it be someone close to him? Meanwhile, Jackie spies on Jess as she heads to Dylan's place and manages to sneak out undetected. She ventures into town, where she learns that Solomon is being held for questioning, and the heat is on the farm, putting the Bevan family under fire.
Bull tries to diffuse the situation when Jackie arrives, hot-headed and demanding answers. He takes her aside while Jess delves into the files and discovers why Jackie was initially excluded from the investigation. The footage from her bodycam reveals her gross negligence, including her lashing out at Bull and striking him after he used information she shared with him to arrest Lydia.
Additionally, we learn that the gloves found on the farm don't match any of the fibers found under Cefin's fingernails. As for Nessa, she was severely burned before her death, but that wasn't the cause of her demise.
The autopsy reveals the presence of soil and plastic particles in her lungs, accompanied by bruising at the back of her neck. It is clear that she was suffocated and met a violent end. Most compellingly, it appears that the modus operandi in both cases is identical. Whoever killed Nessa also took out Cefin. Bull eventually allows Jackie to read the file, but predictably, it's too much for her to handle. Jackie is more convinced than ever that the killer is someone within the village and desires to seek answers herself.
The focus inevitably shifts towards the Bevan farm workers first, and thanks to the boot Bull retrieved from the assailant outside Morgan's house, he also knows that Alfie and the other kids are responsible for breaking into Morgan's property. Ned eventually speaks up here, explaining that he contracted out the fields but shut down the entire waste dumping a few years ago. Apparently, he wasn't dealing with it day to day, which means someone else could well have known about Nessa and stopped the dumping as a result.
Bull is enraged and running low on patience. He heads back over to see Solomon, believing he – or one of the Bevan family – could be the suspect. His emotional involvement here is obvious, and Jess is shocked to hear Bull badger Solomon so harshly and even shout for him to leave too.
Jackie shows up to see Lydia while this is going on, but she's not exactly enthusiastic to see her sister. It brings up old memories and causes her to break down in tears. Unlike the others, Jackie is still living in the past and can't move past Nessa's death. Her presence, stirring up old feelings, is not what the family needs right now, and she's eventually forced out.
That night, the situation took a turn for the worst when Bull learned that Dylan's DNA matched the hair found at Cefin's scene. Morgan appeared, announcing an extreme weather warning and the need to evacuate the village. Bull, overwhelmed with emotion, tried to confront Morgan but was pushed away. He hurriedly gathered his belongings and left.
The next morning, knowing he needed to act quickly, Bull visited Dylan at his place. There, he learned that Dylan and Jackie were dating and that she could corroborate his alibi for the time Cefin died. They'd been dating for about a year, which explained why Jackie had been hesitant to tell him about the pregnancy.
Bull was hesitant to pursue Dylan further, fearing it would compromise Jackie's position, while Jess wanted to explore their solid lead. There was also August, who had been sending cash back to Romania and making deposits in cash for more than a year.
Jess wanted to bring both of them in, so she confronted August about the money. Drawing on her own cultural upbringing in China, she managed to get through to him. She believed he was being blackmailed and wanted the truth. Eventually, August admitted that there was more waste coming into the village but didn't know where it was coming from. A truck came in during low tide every Thursday, and she encouraged him to go up to the causeway to take a look.
At the causeway, Jess and Bull waited for the inbound truck when the tide was low. When Bull found out that Jackie had been at the farm earlier in the day, asking Solomon questions, he headed over to see her. Jackie was a mess, and Bull comforted her as he saw her digging up all the old case files for Nessa. He realized how distraught she was and tried to help, but she ended up cutting her foot on some broken glass.
The villagers realized that the tide wasn't getting lower and that the storm threat was very credible. They were completely cut off, and nobody was coming in or out. The storm would be there imminently, and they needed to find August before it was too late. Jackie joined Bull, but that night, there was another death. August Antonov was found face-down in the rising rainwater, and it became clear that someone was trying to keep things quiet.
