Somewhere on the list of plays I always wanted to see – but never thought I would have the chance – is Mourning Becomes Electra. Eugene O’Neill’s four-hour-plus adaptation of the Oresteia, the trilogy of Greek tragedies by Aeschylus about the return of Agamemnon from the Trojan War, is widely thought too dated and unwieldy for today’s audiences.

I certainly didn’t expect I’d see it in Mount Airy.  And that the Quintessence production would be so stylish and compelling? It’s one of those small miracles the theater sometimes brings.

Written in 1931, Mourning comes at a pivotal point in O’Neill’s career. The melodramas and experimental plays of his youth were behind him. (While these brought him fame and several Pulitzers, many are no longer stage-worthy.) His monumental, more contemplative later plays are still to come.

Mourning represents a link between the two. It is undeniably melodramatic, heavy with plot revelations and hand wringing. O’Neill follows the Oresteia quite faithfully, resetting the action to America immediately following the Civil War, and breaking his own play into three acts – Homecoming, The Hunted, The Haunted – that correspond to the Aeschylus trilogy.

We also find O’Neill probing the emotional bonds of parents and children, a favorite theme that would reach its peak in Long Day’s Journey Into Night. His focus here is the Mannon family – father Ezra, returned from the war, and mother Christine, who during his absence has taken a lover. The legacy of their various betrayals and shortcomings has a crippling effect on their son Orin, and especially their daughter, Lavinia (the Electra figure).

There is also a grandeur of conception to Mourning that prefigures O’Neill’s great, late plays.

I was especially gratified – and, frankly, surprised – at how effectively director Alexander Burns delivers on that sense of size and scope. In his intimate space, he creates a series of vivid stage pictures that are very much large-scale. Burns himself did the scenery, which masterfully uses fragments – shutters, a door – to suggest the huge Mannon house. (John Burkland’s lighting is equally striking.)

The acting, too, is mostly on an epic scale. Sometimes too much so – early on, I worried that the cast was taking the Greek oration tradition too literally, with too many “announcements” and too little conversation. The production would benefit from a few more quiet moments.

On the other hand, it’s thrilling to see a group of actors commit so fully. To watch Janis Dardaris (Christine) at the end of the second act is to experience a rare kind of go-for-broke risk-taking. After all, Mourning  is a melodrama – and this style is absolutely in the play’s interpretive tradition. (One of the few pleasures of the hokey 1947 film version is watching Rosalind Russell and Katina Paxinou go at it.) None of the other actors here quite equal Dardaris’s bravado, but Mattie Hawkinson is an effective Lavinia, and there is a riveting supporting performance by Robert Jason Jackson (Ezra). The rest of the young company does honorable work.

Burns’ makes the intriguing choice to vary the setting – he keeps Homecoming in the Civil War, but moves The Hunted to World War II, and The Haunted to the Korean War. I get the point – that the themes of love and war are timeless, and it pays some surprising dividends in The Hunted, which cleverly evokes Double Indemnity. I don’t think the updating works as well in The Haunted, but frankly this is also the weakest section of O’Neill’s play.

What’s most exciting at Quintessence is Burns’ confidence in the power of Mourning Becomes Electra – and how much that confidence pays off in performance. At Sunday’s matinee, a multigenerational audience seemed absolutely spellbound. By the way, the cast – who gave their all for four hours – had done a performance the night before. Now, that’s dedication!

Through April 27, Quintessence Theatre Group at Sedgwick Theater, 7137 Germantown Ave., 215-987-4450, quintessencetheatre.org