Yes, she’s the title character, and it’s her secret marriage to a commoner that triggers the play’s extravagantly long daisy chain of murders. But the duchess isn’t the real heart of John Webster’s Jacobean classic. That would be Bosola, the hapless soldier who finds himself committing horrific crimes out of–well, it’s complicated, but it has to do with following orders. Funny, sympathetic, weirdly decent, utterly damned, Bosola is the prototype of the modern war criminal: a circumstantial monster. Matt Kozlowski manages this epic character’s endearing qualities but not the darkness. Like practically everyone else in this tepid staging, he fails to express moral violence. Without bold performances, Michael Halberstam’s highly stylized, Bunraku-influenced production ends up looking merely tricked out. Through 7/16: Tue-Fri 8 PM, Sat 5 and 8 PM, Sun 2:30 and 6 PM, Writers’ Theatre, 325 Tudor Ct., Glencoe, 847-242-6000, $40-$57.