The heartbreaking thing about David Mamet's career is that he hasn't written anything as human and tight as the early plays that made him famous: Glengarry Glen Ross and, of course, American Buffalo. Their spare, half-articulate lines can still sound powerful on the tongue of a good actor. If Richard Harder, who plays Teach in Buffalo on the Shelton Theater's new stage, could be cloned three times, Jean Shelton's production would be amazing; as it is, Harder carries the other two actors along. "Teach" is the nickname for a hustler who edges out an innocent boy named Bobby in a scheme with a junk-shop owner, Donny, to swipe a collection of buffalo-head nickels. Harder plays him with a rolling, dangerous street energy, and his edginess communicates more than anything Teach says, which is the whole point of a Mamet character. Joseph Silva is bland and meek enough as Bobby -- I just wanted him to be more intentionally meek, more focused -- and Charles Brumm is shambling enough as Donny, but too sweet-tempered and kind. Both actors need some of Harder's tension in order to nail the language. The show is still funny, but it ends weakly because Teach leaves the stage without trashing Donny's junk shop. Harder -- good as he is -- has to give his climactic speech to thin air instead of tumbling shelves of toasters.