Driven to desperate measures, nurse Cath Hardacre assumes the identity of her best friend, an A&E doctor, and finds work in a struggling emergency department.

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 - does she protect her identity or fall further into the lie?

Ally's personal and professional lives start to fall apart as Karl, who is desperate to prove himself, arrives in Edinburgh.