Jordan Harrison's fanciful tale of an inspired teenage girl, Moll, who invents a machine that can "hear the unhearable" is loaded with clever whimsy--not to mention hilarious sound cues courtesy of Foley artist Scotty Iseri. The crux of this 90-minute fable, directed with a light but sure hand by Damon Kiely, is how Moll (played with winning gusto by Gwendolyn Whiteside) deals with having her machine stolen--and heart broken--by a shape-shifting mercenary. But Harrison throws too many meta screwballs into the mix; a narrator breaks the fourth wall, and a radio play within the play starts spilling over into Moll's adventures, which distances us from her poignant self-discoveries. Still, Kiely's whip-smart cast, Lindsay Jones's terrific sound design, and John Musial's Rube Goldberg set combine to create an often delightful production. Through 3/20: Thu-Fri 8 PM, Sat 5 and 8:30 PM, Sun 3 PM. American Theater Company, 1909 W. Byron, 773-929-1031. $20-$30; industry shows Thu and Sat 5 PM.