The Last Chance (1937)

...TO FIND THE MISSING EVIDENCE THAT WILL PROVE HIS INNOCENCE...

Alan Burmister leaves Devon on a secret gun-running expedition immediately after his engagement to Mary Perrin is announced; he returns at Christmas to find himself accused of the murder of Ivor Connel, a moneylender. Mary's father had always hoped that his daughter would marry John Worrall, a rising barrister. Worrall is briefed for the defence, but when he loses the case and Alan is condemned to penal servitude for life, no one but the judge realises that he has not made use of the best piece of defence evidence...