Just as the movies could never really contain the genius of Orson Welles, neither could the theater. In fact, his astonishing stage career, often described in terms of "a meteoric rise," was more an explosive swell -- of magic, of mayhem, of pure theatrical brinkmanship -- that burst the three walls framing his productions. And in "Moby Dick Rehearsed," an impressive staging of which is now being presented by the American Century Theater, he shattered the imaginary fourth with this, his adaptation of the Melville classic.

Forget Ishmael, Ahab, even the whale: The theater and its umbilical connection to the imagination is the true focus of this exercise in megalomania. As the audience arrives inside the stripped-down black box of Gunston Arts Center's theater, so do the actors and crew, nonchalantly talking to each other and occasionally to us, making us feel like invited guests to what is supposed to be their rehearsal of "King Lear." Enter, then, the company's tyrannical "director" (Charles Matheny), who decides to scrap "Lear" in favor of "Moby Dick," complete with the Nantucket wharf, the good ship Pequod, the open seas, a storm or two and the big fish himself. All on an essentially bare stage.

The hubris almost takes your breath away, but that was Welles -- the original abominable showman.

Jack Marshall -- the real director -- does a sharp job choreographing his cast of 16, using only movement, sailors' songs, a platform, a few benches and scaffolding to lure your imagination into "seeing" every location and atmosphere the script calls for. Ricki Kushner's haunting sound design is almost itself a character. When, for example, we hear Moby Dick finally breaching, I almost believed that something horribly real was coming up through the floor.

There's fine work in the supporting cast, including Timothy Hayes Lynch as Ishmael, Richard Henrich as Starbuck and David Jourdan as Stubb. The remaining ensemble members work well as a seagoing crew. Matheny's Ahab, meanwhile, is a convincing but wrong interpretation. From the start he is, rightly, a man obsessed. But it's all locked up in his head: With every line he speaks, his obsession seems to drift further inside him, away from us. There's nothing of the Welles-style passion thrashing about the surface, spraying everyone nearby.

Which wouldn't be a problem were ACT not billing the show as "Orson Welles' Moby Dick Rehearsed.' " And if Marshall hadn't written extensively in the program of the parallels between Melville's epic tale and Welles's epic life -- the all-consuming pursuit of the unattainable, the willingness to sacrifice anything to get it, the mercurial temperament to which others must always submit. You can't duplicate the way Welles played Ahab, nor would you want to. But if you're going to point up the autobiographical resonance, you'd better explore it in the performance.

Still, the production holds up mostly because of its strengths elsewhere. Also because the author-adapter's shadow looms so large. His only production was destroyed by the critics, and his career, already sinking, went down even faster. Yet he kept trying. You can easily see Welles fighting and defying everyone in his mad, doomed pursuit of some artistic ideal. But you can also imagine him identifying at times with that equally doomed beast -- harpooned for no apparent reason other than jealous hate of his monstrous grandeur. You can see him breaching and being breached: Thar he blows.

Moby Dick Rehearsed, an adaptation of Melville's novel by Orson Welles. Directed by Jack Marshall. Lighting design, David Walden; sound, Ricki Kushner. With Mike Baker, David Elias, Steve Games, John Henry, Joy Jones, Paul Klingenberg, Peter Mendez, Jordan Pulaski, Richard Rohan, John Tweel, Sheldon Wallerstein and Glenn White. Produced by American Century Theater. Through May 24 at Gunston Arts Center, Arlington. Call 703-553-8782. CAPTION: Mike Baker, foreground, is the harpoonist Tashtego and Charles Matheny, rear, is Ahab directing his oarsmen in "Moby Dick Rehearsed."