The quiet coastal town of East Lee, in Suffolk, is thrown into turmoil when Lorraine, a teenage schoolgirl, goes missing and is found murdered. Shock and horror sweep the inhabitants of the town, including the newly merged family of Rosie (Hermione Norris) and her two children Jamie (Alexander Arnold) and Livvy; and her new partner Ben (Martin Clunes) and his two teenage children Bob and Jess. Their new life together is overshadowed by the threat that a killer might be present in this safe seaside town. When Rosie finds a stained pair of trainers hidden in Jamie's room, she suspects it could be blood - could her son really be involved in Lorraine's murder? As the police investigation continues, the emotional turmoil and stress of the tragedy start to cause tension between the two sides of the family. Jamie seeks solace with his dad, David (Paul McGann), but Rosie finds she can't suppress the growing feeling that her son might be guilty of something terrible. With Rob also acting suspiciously, Rosie decides to do her own investigation. What will she discover?