Lantern Theater, St. Stephen's Theater, 10th and Ludlow Sts., through March 8, 569-9700

Keep your eyes on Maggie Siff, who plays the chambermaid Regina in Lantern Theater's ambitious production of Henrik Ibsen's Ghosts (in a translation by Nicholas Rudall).

In the final act of the play, Regina learns about her true parentage, learns that her employer's son, on whom she has an abiding crush, is likely to be an invalid, and learns that marriage with him is impossible. As with her other roles in Philadelphia over the past two years, Siff brings a singular, emotional quirkiness to the role. She brings something else to her character's moment of discovery and disappointment: raw, confused, unprocessed, uninflected, unshaped emotion, pure and not-so-simple.

I single out Siff's performance because it represents what's missing in some of the other performances. Each of the other characters (with the exception of Engstrand, the delightfully hypocritical carpenter, played with élan by Frank X) has a similar moment of life-changing discovery and disappointment at some point in the play. All of the actors register the emotions of their respective characters' moments of discovery; and director Charles McMahon has orchestrated the sequence of events expertly. But rarely do these moments have the type of emotional depth and awesome truthfulness that sends Siff's Regina sailing tearfully and resolutely out the door at the end of her last scene.

Ghosts, Ibsen's savage sequel to A Doll House, depends upon such moments of discovery and understanding, for there is no action, per se, in the play. One year into her marriage, Mrs. Alving, like Nora in A Doll House, walks out on her husband, fleeing to the house and (she hopes) into the arms of her friend Pastor Manders, only to be persuaded by him to return to her husband. But that was 29 years ago. Everything that happens in the play is the consequence of her decision to return - to play the part of a dutiful wife and hide her husband's profligacy from the world for the next 18 years, despite her growing conviction that such idealized notions as wifely duty are bankrupt and untenable.

Nothing actually happens in the play itself: Manders learns the truth of Mrs. Alving's marriage; Mrs. Alving watches as "the sins of the father" are visited upon her son Osvald (in the form of hereditary syphilis); and she realizes from this her own failure to free herself from the ghosts of dead ideas and false ideals.

It's all the more important, then, that the actors bring the most complex and the most palpably real emotions to the only events that do occur during the play: the moments of discovery, realization and belated understanding. And to a certain extent they do. Tim Moyer, in the thankless role of Manders, seems credibly confused when he is told that the marriage he had prided himself on having repaired was a fraud: his mutton-chopped cheeks, along with his spirits, sag as he sinks into stammering impotence. And E. Ashley Izard, as Mrs. Alving, and Joseph Pokorny, as Osvald, use their actors' craft to open the window shades onto their characters' emotional lives.

But it's just not enough. Izard retains a Katherine Hepburn-like brittleness throughout, even in her rawest moments. And Pokorny remains slick and in control, even in his wildest, most distraught moments; Osvald's joie de vivre seems more like smarminess than healthy exuberance, especially in his attraction to Regina. Neither actor ever fully opens the window onto the type of peculiar emotional truth that Siff exposes in her cameo.

Without that, Ibsen's high tragedy teeters on the brink of melodrama. Hell, this is a play in which a character lapses into tertiary syphilis, onstage, as we watch, only a few minutes after he talked about the likelihood of its happening. Nobody said this stuff was easy!

For it to work, the emotions have to be as real as the smoke that wafts into the audience from Osvald's cigar; instead, it's all about as real as the pelting rain outside that magically disappears from the characters' hair and clothing the minute they shake the imaginary water drops from their umbrellas in the doorway.

-Cary M. Mazer