You might think the subtitle of Rinne Groff's play--"A Trick in Four Acts"--refers to a feat of prestidigitation. After all, the main characters are a magician and his assistants; the plot has to do with an attempt to steal the magician's secrets; and, yes, magic tricks are performed. But the real trick is literary: Groff attempts to ring changes on a single metaphor for nearly two hours. And a hokey metaphor at that: "love is magic." Groff spins the conceit out cleverly, but the effort begins to cloy as she becomes ever more self-impressed and eager to display her whimsy. Mikhael Tara Garver's staging for Uma Productions embraces the whimsy when it might have done better to inject some grit. --Tony Adler a Through 5/19: Thu-Sat 7:30 PM, Sun 3 PM, Chopin Theatre, 1543 W. Division, 773-347-1350, $15-$20.