Julie Arnold Lisnet plays a minor role in “The Heiress,” which opened this weekend and runs through Oct. 20 at Penobscot Theatre. As Mrs. Montgomery, who appears solely to give a character reference for her brother, Lisnet’s total stage time must run about 10 minutes, and her lines are minimal. She doesn’t even show up until an hour into the play.

But her performance jolts the evening with an intensity that captures the psychological depth Henry James intended in his novel “Washington Square,” on which this 1947 play by Augustus Goetz and Ruth Goetz is based. The work Lisnet does — the subtle gestures and vocal nuances that fully indicate an internal complexity — is the very stuff you go to theater to get.

Her colleagues often seem to be in a slightly altered version of the same play, which was written as a psychological thriller about a rich girl who is jilted in love by both her father and her suitor. Director Lisa A. Tromovitch has re-envisioned it as a contemporary comedy of manners, and, at least in the funny parts, the humor works quite nicely.

To a large degree, the success of the humor lies in the hands of Brian Berry as Morris Townsend, the gold digger who convinces Catherine of his love for her temperament rather than for her inheritance. Berry looks like Michael J. Fox, and his punchy expressions rouse the same kind of responses Fox gets from TV and film viewers. In short, Berry is comical, and his interactions with Devon Louise Jencks, who is a sweet bunny of a Catherine, can be delightfully amusing.

One can’t help but feel, however, that the spirit of this play is cheated by the laughs. It’s not that this adaptation doesn’t have solidly funny lines; it does and they are intelligent in the restrained fashion of the time. But they are not the heart of this play, and that discrepancy comes up unavoidably in the second act, when the audience must believe that the seriousness of Catherine’s pain has caused her to be bitterly revengeful. At that point, the comedy of the first act challenges the tragedy of the second, and this slackening of dramatic tension does not prepare the audience for a profound ending. It is an uncomfortably fervent wrap-up that makes Catherine look quite pitiful rather than hard-heartedly clever.

“The Heiress” is one of those plays that theatergoers sometimes roll their eyes at because they think it might be dreadfully boring in all its high drama. That’s simply not true. This is a magnificent play — smartly written and amazingly pertinent. But it requires an obedience to James’ graceful understanding of the psychological world, and this is where Tromovitch’s revival makes a departure. The cast is young for the most part, so the overall feel of the plot is of a darling but dim-witted girl, rather than of a quietly bright young woman turned awkward by a deprivation of love from her father. She appears more ignorant than idealistic, which helps with the laughs but steals from the drama.

It might be that Tromovitch wants to win over the audience with the humor that permeates this production. In this regard, she is successful — particularly on opening night, which won the cast a standing ovation.

Finally, this is a play about the excruciating movement from innocence to experience. It’s right to play the humor, but it’s a shame to lose the edge of the theatricality inherent in the harsh lesson. Lisnet gets the right combination and her performance stands out. Muriel Kenderdine, as Catherine’s supportive aunt, is also at home in this milieu. She can be a sparkling delight, but she can also believably shift into dire concern. Amanda Esposito, as the maid, Maria, is cute and spirited, and Sharon Zolper does a fine job as another aunt, though she, as well as the other actresses, would benefit from hairstyles that better represent the period.

David Skigen as Dr. Sloper (Catherine’s father) recites his lines as if for a speech class. He’s formidable in his stances, but has the feel of a textbook rather than a charismatic leader who is also briskly patriarchal. As with Berry and Robert Fields (who plays opposite Becky Young as a loving couple whose relationship foils the central action), Skigen has the distracting habit of nervously putting his hands in his pockets — one of the niggling details that, like the hairstyles, doesn’t seem to fit the era.

Lucia Williams-Young gets the women in pretty gowns and the men in stalwart suits. The opulence of New York’s Washington Square in the 1840s is a tough scene to re-create, but Jay S. Skriletz has done a good job making this a workable set — except that the Sloper doors have a nasty tendency to bang loudly and you would think a household of this standing would have a bit more control over such noises.

Tromovitch’s production has much to enjoy. Still, it’s tempting to wish it had paid more homage to James’ fascinating drama of the mind and the way it twists in the throes of greed and loss.

“The Heiress” will be performed 7 p.m. Thursday, 8 p.m. Friday, 8:30 p.m. Saturday and 2 p.m. Sunday through Oct. 20 at Penobscot Theatre. The show also will run 5 p.m. Oct. 12 and 19. For tickets,