Alvarez is onstage only for a few minutes in each of the two scenes in The Unseen, but he dominates — nay, towers over — both of them like a mad, yet-to-be-deposed dictator. As a secret prison's brutal guard with a heart of... something, he hulks back and forth between two crude cells, and you can't take your eyes off him: a blocky refrigerator of intimidation, shaking the rafters with brutal curses that sound as if it's the first time we've ever heard these words. In Alvarez's grungy toolbox, they have a gripping power that puts most of David Mamet's artful profaners to shame. When he speaks, we all listen, even if we don't want to, as with his squeamish description of the murder of an inmate by removing his eyes and tongue, single-handedly. He still manages to make us laugh, uttering some of the funniest exclamations in this dark comedy; but if you saw this, chances are you slept with one eye open that night.