One of three so-called “problem plays” written by William Shakespeare, Measure for Measure is a dark comedy on the theme of virtue versus sin. “O, what may man within him hide, Though angel on the outward side!” says Vincentio, the Duke, in Act 3, Scene 1. The story concerns the fate of Isabel, a young nun faced with a moral quandary when the deputy, who’s in charge of Vienna in the absence of the Duke, presents her with an unsavory proposition in exchange for saving the life of her soon-to-be-executed brother. The Bard’s ambiguous and challenging play is brought to life by the International Shakespeare Center at The Swan (1213 Parkway Drive), starting with a 7:30 p.m. performance on Friday, Aug. 23, and followed by 7:30 p.m. performances on Aug. 29, 31, and Sept. 6. Sunday matinee performances take place at 2 p.m. on Aug. 25 and Sept. 8. General admission is $25, with discounts available. Tickets can be purchased online at brownpapertickets.com or at the door. A post-show discussion with Measure for Measure director Caryl Farkas and several performers — led by International Shakespeare Center president Robin Williams — takes place at 10 a.m. on Monday, Aug. 26 ($10 at the door). Call 505-466-3533 or visit internationalshakespeare.center for more information.