At first he's a simple man, struggling with the loss of his wife. When his son dies he goes insane, but at some point, presumably because of Rick's intervention, he finds his path from madness back to the world. And he's come back as a pretty cool bad ass! Wielding a staff as quick as any other weapon (which make sense, its quiet and deadly to walkers) he's shied off killing people
Or so we think.
Regardless...he's back and the whole point of this blog post is that you have to watch it, because the actor, Lennie James, has one of the coolest voices I've ever heard.