In the summer of 1952, Joyce and Charlie Savigear are waiting on a railway platform in the quiet English countryside. The siblings have just been released from borstal to start a new life as apprentices at Leventree, an architectural practice with a difference. The architects who've chosen them are Florence and Arthur Mayhood, a married couple motivated to give young offenders second chances. At first, they seem to offer the Savigears a steady path to happiness. But when a dangerous figure from Joyce's past comes knocking, they are lured back to the world they left behind. Is the Mayhoods' good will enough to steer their young apprentices away from danger, or will the darkness of the Savigears' past catch up with them?