Eugene O’Neill tilled the human conscience, unearthing buried anguish, deep-seated loneliness, and hidden aggression. The result? An evening of O’Neill usually features harrowing, no-holds-barred theater; his were the great American tragedies writ large on the stage. The modest American Century Theater, committed to resuscitating great but overlooked 20th-century gems, has taken up early O’Neill with Desire Under the Elms, a dig into the dankness of the human psyche that clocks in at less than two-and-a-half hours. And while American Century’s stark, spare revival uncovers a few moments of incendiary drama, uneven casting and impecunious production values make this a less than wholly fulfilling evening of theater. Elms’ Cabot family is a God-fearing New England clan; they praise and curse the Lord, enunciate his commandments, take to heart their God-given land and the fruit of that rocky plot, hard-won by patriarch Ephraim and coveted by his sons. There’s an ascetic poetry in O’Neill’s plainspoken characters, with their working-class New England dialects and their folksy expressions, but not all the actors are quite up to the weighty task of relaying that poetry. Gray-bearded Kevin Adams displays a rough-hewn wildness as the ornery Ephraim, but with his all-American good looks, Parker Dixon’s brooding youngest son, Eben, can seem a little too golden. And throaty Susan Marie Rhea, as Ephraim’s new wife, Abbie, throws the family into turmoil as she transforms into a wild-eyed 19th-century Jocasta, igniting a volatile triangle that culminates in incest and infanticide. (Desire Under the Elms caused a ruckus in 1925, when a New York district attorney threatened to shut down the Broadway production on account of the “obscene” onstage relationship between Eben and his stepmother.) American Century’s production doesn’t dig into the marrow of these matters, though, and O’Neill’s tragedy, daring in its day, plays like melodrama. Director William Aitkin fits the spare play into Gunston Theater II’s unforgiving black box with little embellishment on an unattractively Spartan set. He keeps the dysfunctional clan navigating bedroom platforms at opposite ends of a dark, bare stage; as for the elms, great brooding trees that O’Neill envisioned hanging oppressively over the Cabot house, like “exhausted women resting their sagging breasts and hands and hair on its roof”? They’ve been excised, leaving the production, save for a few slate rocks, bereft of the foreboding that overshadows this American-made epic.