In a month that has seen a group of Broadway pros poised to back up two reality-show contestants in “Grease” and reports of Whitney Houston potentially supplanting Audra McDonald in a “Cat on a Hot Tin Roof” revival, the casting gods appeared to have come to their senses with the arrival of Brian Dennehy and Christopher Plummer in “Inherit the Wind.” The musty but surprisingly durable 1955 dramatization of the Scopes monkey trial is tailor-made for these two titans. Who better than Mr. Dennehy, with his deceptively harmless bluster, to play the avuncular, shambling man of the people whom the authors Jerome Lawrence and Robert E. Lee based on Clarence Darrow? And if you’re looking for a dogma-spouting model of rectitude, á la Scopes prosecutor William Jennings Bryan, how could Mr. Plummer’s steely gravitas be improved upon?

Before you read any further, let alone head over to the Lyceum Theatre, you should know that director Doug Hughes has got it all backward. Mr. Plummer is playing not the fiery Matthew Harrison Brady but the folksy Henry Drummond, while Mr. Dennehy is forced to rein in his Irish charm and get all starchy as Brady. Or at least half backward: While Mr. Hughes’s no-nonsense production of this chestnut relinquishes some of its punch, in part because of Mr. Dennehy’s inability to play to his strengths, Mr. Plummer wears his roomier, gaudier role with the casual precision of a bespoke suit.

He has a head start in that Drummond is by far the showier and more sympathetic part. Lawrence and Lee, who elided and added facts to boost their cause, make no claims of evenhandedness. Rather, they use the battle of evolution versus creationism to frame a tale of 20th-century rationalism, represented by Drummond and the fast-talking Baltimore reporter E.K. Hornbeck (a fidgety Denis O’Hare), wittily dragging the bigots and “clockstoppers” of the previous era into the modern day. Brady, a three-time presidential candidate, may enjoy the adoration of Hillsboro, a Southern town that the derisive Hornbeck sums up as “the buckle on the Bible Belt.” Seen through the authors’ progressive prism, though, he is less a true adversary and more a temporary obstacle.

Their faith was perhaps optimistic, as current events have shown. (“You don’t suppose this kind of thing is ever finished, do you?” Drummond asks his client at the end of the trial, eliciting a knowing laugh from the audience.) The program notes persist in coyly giving the play’s setting as “not too long ago,” as if setting a political work too firmly in the concrete past would deny it its topical punch. All the same, Mr. Hughes’s musical and sartorial choices — to say nothing of the prominently displayed 48-state American flag — are entirely consistent with the 1920s.

The staging also sticks with the tried-and-true, at least during the extended trial scenes. (A few experimental flashes, in which Brian MacDevitt’s lighting grows ominous and the townsfolk gather in rigid formations, feel out of place.) Mr. Hughes, who typically gravitates toward more intimate dramas (“Doubt,” “Frozen”), arrays the 30 cast members all over Santo Loquasto’s stately courtroom set, where they take in the still-entertaining proceedings alongside a few dozen audience members who have been seated in the onstage risers.

Mr. Hughes’s vaunted reputation as an actor’s director takes a bit of a hit here. While Byron Jennings’s apocalyptic preacher and Jordan Lage’s mirthless assistant prosecutor find shadings within the authors’ limited palette, Benjamin Walker and Maggie Lacey are stiff and pinched as the accused teacher and his girlfriend, respectively. Nobody could accuse Mr. O’Hare, meanwhile, of stiffness. Fussing with any prop he can get his mitts on, stretching his (admittedly purple) dialogue in all directions, Mr. O’Hare trots out his now-familiar mannerisms to little effect. When Drummond finally blasts Hornbeck for being so tiresome, the reprimand is long overdue.

Mr. Plummer plays with the tempos of his lines, too, but does so within the parameters of his character. He also conveys the act of thinking on his feet as well as any actor working, and he has added an effective down-home drawl to his extensive vocal repertoire. (The drawl thickens slightly as he corners yet another witness, savoring the inevitable snap of his latest lawyerly coup.) The outcome of the trial is never really in question, but Mr. Plummer’s wily, beautifully realized portrayal plants the tiniest seed of doubt into the audience’s minds.

He and Mr. Dennehy share two dynamic scenes: A nicely staged moment of nostalgia in Act 1 and a thunderous Act 2 cross-examination in which Drummond puts Bryan himself on the stand. Drummond has the upper hand in each of these sequences, and yet Mr. Dennehy scores his share of points. Ironically, this stems in part from his refusal to give up the characteristics that would have made him such a good Drummond. Brady’s pointed mispronunciation of “evolution” as “evil-ution” is softer, less pointed than usual, and even when Brady finds his own bedrock faith shaken by his adversary’s courtroom ploys, Mr. Dennehy never lets the twinkle totally disappear from his eye.

This creates a strange hall-of-mirrors effect. Rather than watch two formidable adversaries slug it out, we’re left with the image of a good guy doing battle with his evil doppelgänger, the sort of thing you might see in a superhero movie. And when does the evil doppelgänger ever stand a chance?

Perhaps what’s needed is for the two stars to dip into that time-honored theatrical gimmick of swapping roles, like Laurence Olivier famously did with John Gielgud (in “Romeo and Juliet”) and Anthony Quinn (in “Becket”). Or like Nathan Lane and Matthew Broderick threatened to do in “The Odd Couple,” although the problem there was that both actors were essentially Felix Ungers. The biggest surprise in this “Inherit the Wind” — a play that, for all its hoary charms, boasts very few surprises — is that Mr. Hughes winds up with two Henry Drummonds on his hands. No matter how much you may prefer folksy humanists to dogmatic clock-stoppers, that’s one too many.

Open run (149 W. 45th St., between Sixth and Seventh avenues, 212-239-6200).