In Machine Gun Preacher, Gerard Butler portrays Sam Childers, a drug-dealing biker destined for an early grave before unexpectedly finding himself in a Sudanese war zone, charged with protecting hundreds of orphaned children.

The Scottish actor, who spent more than a year preparing for the role, says playing Childers ranks among his most challenging, yet also incredibly rewarding.

Gerard Butler and co-star Michelle Monaghan, who plays Childers's wife Lynn, spoke to CBC News about filming the demanding and emotional story.