Destined to be Dauntless

There's more to the rivalry between Eric and Four than a mark on a scoreboard.
What made Eric so malicious and violent? Four so distant and unapproachable? What turned them so irrevocably against one another?
Between two opposing males there is inevitably a woman at the centre of it, but what happened to her?

Tobias Eaton and Isabelle Jones defected to Dauntless two Years before Tris Prior unwittingly kicked off the Divergent war. He left to escape his father, her to the only place she'd long known she would fit in and finally be free to rediscover the self she had buried for so long.
Eric Coulter left Erudite to join the faction he had been destined to join since childhood and in doing so rediscovered a piece of his past he thought lost.
Isabelle and Eric are drawn together through their shared past, leaving Tobias out in the cold, but will Isabelle every truly be able to walk away from her closest friend.

New Leader Max is making big changes in Dauntless but he's not acting alone, Erudite are starting the factions on a path that will lead to civil war but what part will Eric, Tobias, and Isabelle play.