An innocent man goes to prison. It takes his selfless sister 18 years of single-minded dedication to exonerate him. Telling an unbelievably harrowing true story, “Conviction” would never have worked as pure fiction.

Part sibling love story, part justice system expose and part empowerment drama, this effective piece is dependent on the facts of a compelling real-life travesty and the quiet heroics it inspired. Without that context, despite two potent anchoring performances by Hilary Swank and Sam Rockwell, it would have seemed more boilerplate.