Prison officer Leigh lives for her job at Long Marsh men's prison. But when mouthy young Rose arrives, fresh out of training, C Wing will never be the same again.

Will Leigh cross the line between officer and criminal? Rose carries out a dangerous mission, and finds herself trapped in a potentially deadly double bind.

Leigh becomes increasingly isolated from her sceptical colleagues. A guilt-ridden Rose takes a chance to make amends. Toby's suspicions lead him to his own investigations.

With C Wing on lockdown, the prisoners' mental health reaches crisis point in an under-resourced and chaotic system. Meanwhile, Rose sees an opportunity, and Toby threatens to escalate his suspicions.

As Long Marsh comes under the spotlight, life on the tense and paranoid C Wing is altered forever - and everyone is a suspect