The film is based on the the life of Sam Childers, an ex biker, drug user and generally all round bad egg, who finds god and sets up a mission in south Sudan to help children who are orphaned, abducted or affected by the rebel army of Joseph Kony (http://en.wikipedia.org/wiki/Joseph_Kony).
The movie starts with his last spell in prison and how he finds out that his wife has given up her job as a stripper now she has found god, he initially returns to his old ways but after a violent incident one night he realizes he has reached rock bottom and agrees to go with his Wife, Mother and Daughter to church and whilst there he finds God and starts to change his life by getting a blue collar job, supporting his wife and being the father his daughter deserves.
He eventually starts a successful building firm, builds his family a home and also builds a church for people "like him" eg. bikers, down and outers etc..., after a choice meeting with a visiting preacher he learns about the problems in Africa and goes to Uganda to help build, whilst building he meets 2 soldiers who agree to show around, they take him to South Sudan where he see's and witnesses the problem first hand, this touches his heart and becomes his mission to help children.
I have only touched briefly, but his mission is inspirational and is a testament to what one motivated human being can do.