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, whilst Abby decides to turn the tables on The Driver by making a last-minute decision to take the train off the mainline. As Joe closes in on the enemy within and Abby manages to catch the sleeper in her trap, will the police be able to get there in time?

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, whilst working out whether or not to follow Saj's orders or put his faith in his punch-drunk fellow passengers instead. Could retired train driver Fraser's audacious plan really work?