A newly hired guard at a Spanish penitentiary (Alberto Ammann) gets knocked out by falling plaster during orientation; by the time he regains consciousness, the prisoners are rioting, but he manages to pass himself off as an inmate and becomes the protege of the rebellion’s leader (persuasive tough guy Luis Tosar). The plot takes some increasingly unlikely turns in the third act, but director Daniel Monzon more than compensates with gritty prison atmosphere and a superbly intimidating cast of plug uglies. I wouldn’t call this 2009 feature art, but it’s good fun and an effective antidote to sentimental schlock like The Shawshank Redemption. In Spanish with subtitles.