Nightsleeper, Episode 4

A tense premiere. When Joe, an off-duty police officer travelling on the Glasgow to London sleeper train, realises that someone is attempting to gain control and drive it remotely, he calls Abby for help.

When the cyber attack on the rail network prevents Abby from seeing the obstacles in the sleeper's path, she realises that she's in a race against time to avert disaster.

When they realise that one of the passengers may be armed and operating in league with the hackers, Joe desperately tries to work out who he can trust.

With the passengers turning on each other in the aftermath of tragedy, Abby desperately attempts to rally the traumatised Joe and persuade him to take back control.

As Hud and Miller interrogate Abby about her past, Saj realises that this is his shot at the big-time and decides to try and stop the train his way. Joe, meanwhile, must deal with the deadly aftermath of the shooting.

A tense and thrilling series finale. Back in charge, Abby's convinced she now knows how to stop the remaining carriages, but with Joe out of contact, both of them are running out of time.