Cath's best friend Dr Ally Sutton, an A&E doctor, is emigrating to New Zealand with her new husband. At a party, Cath finds Ally's discarded paperwork and decides to steal her best friend's identity.

Cath finds herself falling for Andy and wonders how can she keep hold of the perfect man when she is living a lie; an encounter with someone from her past threatens to expose her secret.

Following his discovery, Andy has a decision to make; a fatal error at work backs Ally into a corner, she must decide whether to protect her identity or fall further into the lie.

Ally's personal and professional life begins to fall apart; Karl heads up to Edinburgh, desperate to take Molly back to Sheffield.

Jamie McCain is recovering from a spinal injury that has left him paralyzed. When patients on his ward start dying unexpectedly around him, he faces a new enemy. He believes the deaths are suspicious, but his investigation is dangerous and difficult.

Jamie continues to disrupt the unit with his recurring night terrors; as he obsessively searches for the truth, his behavior becomes increasingly erratic, and it is unclear whether the threat is real or a product of his imagination.