It has been said that long before a play goes into rehearsals, casting has determined its fate. That certainly is true of the revival of Tennessee Williams' 1961 drama "The Night of the Iguana," which opened a four-week pre-Broadway tryout on Wednesday at the Morris A. Mechanic Theatre. Its doom was sealed the day they signed French film star Jeanne Moreau for what turns out to be a thoroughly misguided stage debut in the English language.

Mesmerizing as she can be on film, Moreau is wrong -- dead wrong -- for the role of Hannah Jelkes, the gallant Nantucket spinster who washes up in a ramshackle Mexican resort with her 97-year-old grandfather. From her first entrance (for which she has been costumed to look like Big Blue Riding Hood) to her final stilted gesture of heartbreak (borrowed, it would appear, from a Racine tragedy), the actress strikes nothing but wrong notes.

Fatally complicating a bad situation, Moreau's costar, Michael Moriarty, is scarcely more appropriate as the Rev. T. Lawrence Shannon, whose life also is unraveling on that steamy veranda "between the sky and the stillwater beach." Since the two performers must carry the burden of Williams' script -- indeed, the third act consists almost entirely of her ministering to his sweaty demons -- the miscasting qualifies as a flagrant act of sabotage.

That Williams deserves better is almost too painfully obvious to note. In his lifetime, he was regularly hailed as America's greatest living playwright -- a qualification made in deference to Eugene O'Neill. Now that Williams is dead, it seems time to acknowledge outright that he simply was (and is) our finest playwright ever -- an indomitable nightingale to O'Neill's all-too-often earthbound eagle.

"Night of the Iguana" springs from one of his ripest periods, when his writing was illuminated by flashes of divine lightning. The play is as hot and lush as the tropical rain forest in which it is set. Like most of his dramas, it concerns the lost and the wretched, but it throbs with compassion for them and their endurance in a hostile world. If God was too violent and quixotic to command Williams' unwavering faith, in "Night of the Iguana" he found something else to believe in: the passing solace human beings sometimes extend to one another in the darkness of their misery. Like Hannah, he took consolation from the "broken gates between people so they can reach each other, even if it's just for one night only."

The play is a relentless search for those broken gates by characters who seemingly have nothing more in common than their shipwrecked state. The dissolute Shannon has just been deposed from his position as tour guide by a busload of irate Baptist ladies. Hannah, who barely ekes out an itinerant living by doing portrait sketches, is penniless, and her grandfather (Roy Dotrice), "the oldest living and practicing poet on earth," is a rasp away from death. Maxine (Eileen Brennan), the blowzy proprietor of the run-down hotel, survives mainly on rum-cocoas and trysts with the Mexican help.

From the sordidness of their accumulated plights, Williams spins a drama of intense lyricism. And it is here that the production, directed by Arthur Sherman, goes hopelessly awry. Seductive as her delivery is in French, Moreau's English is characterized by broken cadences, misplaced accents and, occasionally, bald mispronunciations. To entrust Williams' sinuous poetry to her is like giving fine china to a fullback: a guarantee of breakage. Hannah is one of Williams' most ethereal creations, but the character accords not at all with Moreau's earthy world-weariness. Garbed in a multilayered kimono in the last act, Moreau is less a bending willow than the sturdy figurehead on the prow of a ship.

Moriarty, who now seems able to play only terminal basket cases, strips Shannon of any sexual appeal. The mumbled performance starts out small and fussy, and dwindles from there. You'll find no dramatic grandeur to his neuroticism, just a profusion of peevish twitches and tics through which a machete could not hack a path. One cannot imagine a broken gate between these two performers. They are separated by a concrete wall.

The evening's chief redemption is provided by Brennan and Dotrice, who are so vivid in their roles that "Night of the Iguana" becomes a play about an ancient poet struggling to finish one last poem before he dies, and a gaudy innkeeper trying to keep her shabby resort from bankruptcy. As "an infant in his nineties," Dotrice draws a touching portrait of old age -- chivalrous in his senility, sweet in his absurdity. Scratching her bare midriff and sauntering indolently across the veranda, Brennan gives heart and a wry wit to Maxine. Whenever these two leave the stage, they take with them our battered hopes that the strength of Williams' vision may miraculously (mir-a-COO-lous-ly, as Moreau says it) prevail.

The supporting players offer no consolations. And Oliver Smith's flamboyant set, rakishly pitched at an angle, mocks the absence of drama unfolding within it. Williams' legacy is too precious to manhandle like this. Moreau and Moriarty will no doubt go on to other projects. But in the face of this debacle, "The Night of the Iguana" probably won't get a major revival for another decade. That's the real shame.

The Night of the Iguana. By Tennessee Williams. Directed by Arthur sherman. scenery, Oliver Smith; costumes, Lucinda Ballard; lighting, Feder. With Jeanne Moreau, Michael Moriarty, Eileen Brennan, Roy Dotrice, Penelope Allen, Marita Geraghty. At Baltimore's Morris A. Mechanic Theatre through Nov. 10.