
When hackers send a train, going from Glasgow to London, hurtling towards death and destruction, two strangers try to stop it before it meets its final destination.

Abby is convinced that she knows how to stop the remaining carriages; however, with Joe out of contact and time running out, it might be too late for those hurtling towards the end of the line.

Joe tries to deal with the fallout from the shock shooting, while deciding whether to put his faith in other passengers; Miller and Hud interrogate Abby.

While Hud's shocking attempt to stop the train his way threatens to end in disaster, Abby is stunned to discover that Joe may be in even more danger than any of them realised.

Realizing that someone on board may be working with the hackers, Joe turns his attention to his fellow passengers, while Abby stuns her colleagues by taking the train off the mainline.