After meeting the twins' parents, Lisa is shocked to discover that her connection to the family might be more than just professional. As the complications within the investigation grow, the hunt is on to find the twins before it's too late. Lisa must also deal with her own family's problems when daughter Abbie is suspended from school.

With the Meredith family reeling from Dylan's death and Sean's arrest, Lisa is charged with finding his alibi and makes a game-changing discovery. Suspicions are raised about another Morecambe resident's involvement with the twins and the police rush to find them. Abbie grows closer to newcomer Vincent, whilst Rob agrees to take on a risky dare. Frustrated by the police investigation, Sean takes matters into his own hands.

When main suspect Nick goes missing, Lisa is concerned about Sean's possible involvement. The discovery of a key piece of evidence provokes a number of new theories and the police begin to look more closely at other members of the Meredith family. Abbie falls deeper into Vincent's world, bringing Sam with her. Meanwhile, Sean's vigilante justice leads him down a dangerous path.

With Nick seriously injured in hospital, Lisa furiously seeks out Sean, whilst Med feels increasingly sidelined. Sean's revelations lead the team to suspect Nick might have vital information about Holly and Dylan and they desperately wait for him to regain consciousness. Meanwhile, Rob attempts to leave the online forum, but finds it not as easy as he had hoped, and Sam tries to offer Abbie a way out from Vincent. Lisa's focus, though, is entirely on the investigation and she's increasingly convinced by Sean's claims that Nick knows more than he's told her. All Lisa can do is hope that he survives so that she can find out.

A confession to Lisa shines a possible new light on Dylan's killer. Abbie has a terrifying experience with some local junkies, and Rob's escalating actions begin to impact on his family. Med starts to suspect Lisa is hiding something from him and begins to investigate by himself.

Despite Holly's confession that she killed her brother, the team are convinced there's more to the story than she's telling them. Keen to get to the truth, Manning and Med question Holly about the mysterious other person present when Dylan died. Lisa struggles to accept her suspension from the force after the reveal of her secret, but with everything at stake, will she still be able to bring Dylan's killer to justice from the sidelines?