Slowly, slowly, “The Passenger” (1975) drives Jack Nicholson all over the map with a trunk full of ambiguity in tow. He plays Locke, a journalist gathering documentary footage in deepest post-colonial Africa. When his hotel mate, a mysterious British businessman, drops dead from a heart attack, Locke assumes his identity and embarks on the road to nowhere, pausing en route for a sequence of inscrutably metaphoric engagements with Euro-formalist tableaux.

“I prefer men to landscapes,” says the dead Brit in a flashback sequence ingeniously constructed by the director, Michelangelo Antonioni, who prefers things the other way around. Architecture dwarfs character in “The Passenger,” no mean feat considering the main characters are played by the iconic Mr. Nicholson and foxy Maria Schneider, fresh off her scintillating turn in “Last Tango in Paris.”

She is credited as “the girl,” and her function in the film lives up to the generalization. Encountered by Locke in the foyer of Gaudi’s undulating Casa Mila, she promptly joins him for, what? A postmodern drift through time and space? An existential thriller? Psycho-spiritual allegory? Formalist picaresque?

Returned to theaters today for a 30th anniversary re-release, “The Passenger” is a classic exercise in the mid-’70s cinema of “huh”? Anyone who knows the film through the shoddy full-frame VHS versions kicking around your hipper video stores will relish this chance for a clear view at its opacities.

The blank look on Mr. Nicholson’s face is by design. Mr. Antonioni provides no key to his Locke; “The Passenger” is star vehicle as black hole. Without getting highfalutin about it – the movie will enable any theoretical flight of fancy you desire – we might see Locke as a man grown bored with his life who stumbles on an unexpected exit and simply walks out. Of course it’s not so simple as that; the movie is explicitly (and yet vaguely) political, metaphysical, allegorical.

“The Passenger” is symbolist cinema, to be decoded as you wish. It’s the composition that counts, and Mr. Antonioni is no amateur.He has a nifty habit of pulling the cinematography down from the ceiling, where it had latched itself onto some worthy surface, and gliding it back into the action of the plot. It’s not quite as if he were condescending to join his own story, but the thriller mechanism feels designed to tether a buoyant abstract impulse that would much rather float off into space.

The dead businessman was a gunrunner dedicated to Third World revolutions. There is a widow in London (Jenny Runacre as Rachel) who comes to suspect Locke alive, and begins to peruse. These things are significant – to a point. And the point is the legendary penultimate shot, a slow burning tour de force in which the camera does impossible things, impossibly controlled. All intellectual tease, “The Passenger” finally gets off, climaxing with a vengeance (both literal and metaphoric).Thirty years or two hours, it’s worth the wait.