Based on the infamous "Great Train Robbery," this film follows Paul Clifton (Stanley Baker) as he forms a team to carry out an ambitious heist of cash from a government mail train traveling from Scotland to London. Clifton feels it necessary to add incarcerated money expert Robinson (Frank Finlay) to the group, so he organizes a jailbreak to free him as well. Although the theft succeeds, the criminals are still hounded by Scotland Yard detective Langdon (James Booth).