Set on a sleeper train traveling from Glasgow to London, a government agency desperately tries to intervene in the rapidly-escalating events onboard. Can two people who've never met, one on the train and one not, work together to save the lives of its disparate group of passengers as the Heart of Britain service hurtles towards what might quite literally be its final destination?
When a passenger realises that someone is attempting to hack his train, he makes a desperate call for help. But can two total strangers work together to get everyone off in time?
Whilst a desperate Joe considers going to extreme lengths to leave the sleeper, an under-fire Abby starts to realise that she has as many obstacles in her path as the train does.
Realising that someone onboard may be working with the hackers, Joe turns his attention to his fellow passengers, whilst Abby stuns her colleagues by taking the train off the mainline.
Whilst Hud's shock 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.
As Hud and Miller interrogate Abby, Joe tries to deal with the fallout to the shock shooting whilst deciding whether or not to put his faith in Saj or the other passengers.
Abby's convinced she knows how to stop the remaining carriages, but with Joe out of contact and almost out of time, is it too late for those hurtling towards the end of the line?
