Two families get ready for Thanksgiving dinner, yet the scene is foreboding and ominous. The camera leers outside the house like a voyeur, and the drab light drains the scene of any holiday spirit. We already know something terrible will happen, and soon. This is the introduction for Prisoners, the new thriller by French-Canadian director Denis Villeneuve. His Hollywood debut is dark and relentless, complete with sinister motives and ugly violence. It’s also utterly compelling, even if its power wanes in the days after watching it.