Viola Davis, best known for her Oscar-nominated role in ‘The Help,’ signed on for the cast of ‘Prisoners‘ on Saturday. The thriller already has big names attached, like Hugh Jackman, Paul Dano, Jake Gyllenhaal and Melissa Leo. The flick is pitched as ‘Mystic River‘ meets ‘Se7en.’ After his six-year-old daughter and her friend are kidnapped, a small town carpenter butts heads with a young, brash detective in charge of the investigation. Feeling failed by the law, he captures the man he believes responsible, holding him captive in a desperate attempt to find out what he did with the girls, whom he’s convinced are still alive. But the further he’s forced to go to get the man to confess, the closer he comes to losing his soul.