The Scapegoat; by Daphne Du Maurier.

The eternal fascinating of the theme of two people who are identical in looks and as different in character as can be - the scoundrel robs the gentleman scholar and the latter has nothing possible but to assume the life of the former for now, and then the scoundrel returns when he has destroyed the other guy's life too, while the good one has been rebuilding the lives of all those that the scoundrel had destroyed - and yet, the good one found only gratitude, while the scoundrel was loved by his dog and his lover, the only two who knew the difference. Now the good guy has to go try to rebuild his own life, from scratch, an impossible task.

Another one from the writer that goes straight to heart.