In Sam Shepard's surrealistic 1974 drama, "Geography of a Horse Dreamer" (at Source Theatre's Main Stage), a cowboy named Cody is held prisoner by a group of thugs who prize his ability to predict horse race winners in his dreams. The trouble is, Cody hasn't been doing so well lately -- "The dreams are jagged," he explains, "I get a fuzzy picture" -- and the red-carpet conditions of his incarceration have deteriorated dramatically.

When he's not manacled to a bed in a shoddy hotel room, his captors throw him about like a medicine ball or force knockout pills down his throat. But even greater humiliation is in store. Given Cody's declining luck with the horses, Fingers, the kingpin of the gang, orders him to start "dreaming dogs" instead. And if results are not forthcoming, waiting in the wings is a doctor willing to undertake some grisly surgical experiments to revive Cody's magic.

The play can be interpreted as a parable of the visionary artist in an exploitative society. ("You got the genius," snarls one of Cody's keepers, disparagingly. "Somebody else got the power. That's how it always is.") But it is just as easily viewed as a bizarre horror story, a nightmare game of cowboys and gangsters. Source's director, Phil Setren, opts for the latter, accentuating the rough and tumble aspects of the play and its bone-crunching energy.

The slam-bang approach makes for a viscerally direct evening although it also overwhelms the strains of mysticism and totemism that weave through this disturbing work. In a cast that is adequate for the most part, Tomas Kearney stands out with a subtly shaded performance as one of Cody's strong-armed but dimwitted keepers. Set designer Jeffrey Cripps Morgan packs a surprising number of levels, catwalks and cubbyholes onto the tiny stage, thereby enhancing the claustrophobic destiny of a horse dreamer whose dreams are vanishing along with the wide-open spaces that once inspired them.

Geography of a Horse Dreamer, by Sam Shepard. Directed by Phil Setren. Set, Jeffrey Cripps Morgan; lighting, Jennifer Garrett; costumes, Paul Cunzeman. With John Patrick McCarthy, Tomas Kearney, Jim Hicks, Lawrence Lerer, Samuel Millman. At the Source Theatre Main Stage through May 24.