Fatal choices ignite instantly in John Ford's The Broken Heart. Ithocles is a soldier. His sister Penthea gets engaged, but Ithocles disdains her fiancé's family, so he marries Penthea off to another man. In one blind move, he ruins his sister's life and creates furious vengeance in Orgilus, the jilted man. A powder-line of tragic events starts smoldering toward vicious detonation.

The Broken Heart, a sneakily devastating masterpiece written in the generation after Shakespeare (around 1628), is running through April 23 at the Quintessence Theatre Group. It's worth seeing if just for the experience. The Quintessence production is good enough to give a sense of it, but uneven performances, in a drama demanding tip-top acting, mean this Broken Heart is not of the best.

It is rarely done in this country, and having seen it now (for the first time), I wonder why. There's plenty to appeal to a contemporary company: It's a surprisingly modern ensemble piece, with good roles for men and women. And there's no copyright.

It is also a fugue of death and fate. No bad guys or good guys -- only people with varying degrees of self-misunderstanding. Ensnared in impossible plights, Ford's people lingeringly voice their agony, in lines that are plain (compared to Shakespeare) yet poetic, with silken tension. He has an early modern fascination with psychology, especially how we never really get over our traumas: "Souls sunk in sorrows never are without 'em," as Orgilus tells us.

All applause and honor to Quintessence. They are dedicated to doing the classics with attention to what's written, and bravo to that. Director Alexander Burns stresses bare-stage clarity (I liked the introductory dances at the beginning), clear characterization, and clever lighting by David Sexton, to direct us to turning points, realizations, crossroads. (Some audience members were puzzling over the snaky synopsis in the Playbill, and, really, you don't need it: The play is so consecutive and inevitable we can't get out of the way of understanding the action.)

Yet I long to see the play done better. Best reader among the actors is Gregory Isaac as the insanely jealous Bassanes. With his beautiful voice and mastery of the poetry, he creates a Bassanes reminiscent of Leontes of The Winter's Tale: "Swarms of confusions huddle in my thoughts." Dana Kreitz as his maid Grausis was funny and an audience favorite.

But Ithocles (Daniel Miller) is far too booming to bring us in, even later in his role, when he starts to see what he's done. Orgilus (Josh Carpenter) has his moments but is strained; restraint in his violent grief, more dynamics, more buildup, would have done better. Penthea is one of the hardest of female roles, and Mattie Hawkinson gives a good account, especially in her tortured facedown with brother Orgilus in Act 2, when she laments "a rape done on my truth."  But the terrifying Act 4 is the test of Penthea, and here, too, there is strain.

I did like Ebony Pullum as Calantha, especially when she throws a ring publicly to a man she should not love. Regal, assured of herself, reckless, she has fate written all over her. The deaths in this play -- death by starvation, death by dancing, death in a chair -- are perverse yet emblematic. Ford seems to ask: See what happens? When you're human and full of passions? And can't see the future? Like anyone?

The Broken Heart. Through April 23 at Quintessence Theatre Group, 7137 Germantown Ave. Tickets: $15-$40. Information: 215-987-4450, quintessencetheatre.org.