Perhaps few institutions, seen from outside, appear more magical, ambiguous and mysterious than the Catholic Church. But without selling short its great big subject, "Mass Appeal" has exactly what the title suggests.

Bill C. Davis' script for two actors -- a hail-fellow-well-met parish priest trying to tame a fiery, impolitic seminarian -- is a marvel of snappy dialogue and sharp dramaturgy. Though not quite so sharp and snappy, the Manhattan Theater Club's touring production at Ford's Theater, directed by Geraldine Fitzgerald, does well by the play.

The bushy-browed Milo O'Shea brings bluff good cheer and jaded world-weariness to Father Tim Farley -- a dipsomaniac with a Mercedes -- a role he created in 1980. O'Shea's performance is miraculously expressive, whether he's guzzling burgundy, charming the socks off parishoners as "the most tactful priest in the diocese," weeping with self-pity or exploding in anger.

Adam Redfield, by no means inept as the troublesome seminarian Mark Dolson, seems stiff and poker-faced by comparison, but does little harm to this fable of faith. As things turn out, it's the seminarian who has it, the priest who has lost it.

The play is set in the Church of St. Francis and Father Farley's study -- the set at Ford's has a prefab look -- where the two challenge, attack and eventually change each other. Put into Farley's care by the seminary's monsignor, Dolson chides his would-be teacher for hypocrisy and cowardice -- accusing him, among other things, of "song and dance theology." The Church's efforts to make faith palatable -- as with Farley telling jokes from the pulpit -- is one of the playwright's themes.

"I took a stand," Mark says proudly, after championing women priests during one of Farley's trendy "dialogue sermons."

"You did not take a stand," the padre replies. "You took a grandstand."

Soon after, Mark becomes the victim of his own pious honesty, hurting his chances for the priesthood, and Farley must decide whether to risk his rank to help him. All that, and more, makes for engaging entertainment. MASS APPEAL -- At Ford's Theater through April 3.