Charmian meets Ronnie Biggs on a train. As Ronnie is a carpenter and petty criminal, Charmian's father, a headmaster, does not approve and forbids her to see him. In love, Charmian leaves home, steals from her employer and goes on the run with Ronnie and his best friend Mike. When captured, Biggs is imprisoned and Charmian is given a suspended sentence. On release, Charmian and Ronnie marry, her pregnancy forcing her father's approval. Going straight but needing money, unbeknownst to Charmian, Ronnie is drawn into Bruce Reynolds plans for the Great Train Robbery.