They say Oscar Zeta Acosta disappeared off the coast of Mazatlan sometime in 1974. Vanished off the map. After years of deep-doodoo drug capering and ballsy Brown Power barristering, the legendary Acosta offed himself into the deep blue murk of one too many strange trips, leaving -- in the words of Hunter S. Thompson -- a "shitrain" of drug-hit theories and Houdini vagaries in his wake.

This year marks the 25th anniversary of the Brown Buffalo's fateful trip, a quarter-century since "witnesses" saw him board a boat and head out into the ocean. And twenty-five years later, his disappearance is still unresolved. No death certificate, no letters home, no clues, no body. Over the years, the fabled Dr. Gonzo of Thompson's Fear and Loathing in Las Vegas -- a real-life attorney whose on-the-street and in-the-courtroom persona was as surreal as his Brown Buffalo alter-ego -- has become something of an American Loch Ness monster. His legacy lives through various unsubstantiated sightings, through his writings, and through the bizarre theories that still abound regarding "Whatever Happened to Oscar Acosta"?

Some believe the civil rights attorney was shot during a dope deal gone bad. Others believe he suffered a final nervous breakdown, succumbing to the damnation of all those years of drugs and debauchery. Others, like his 39-year-old son Marco, don't speculate anymore. They simply accept that the messianic bison's fate remains one of the more schizoid mysteries of American subculture.

"The body was never found, but we surmise that probably, knowing the people he was involved with, he ended up mouthing off, getting into a fight, and getting killed," says the younger Acosta, a San Francisco-based vocational counselor and musician who is almost as hard to track down as his father. "You're not exactly going to call the FBI and say, 'Hey, my dad disappeared dealing drugs. Can you find him?'"

No, that wouldn't do. Especially considering that Oscar Zeta Acosta spent half his life fighting the law and the other half fleeing it.

A radical attorney, renowned dope fiend and colossal bleeding heart, Acosta was a man of extreme action. He was a judiciary revolutionary, as prone to setting on fire the lawns of Los Angeles judges as he was to playing clarinet for the Panamanian leper colony where he once served as a missionary. When Oscar was bad he was baaaaaad. But when he was good, man was he good.

As an early leader of California's Brown Power movement in the late '60s and early '70s, he fought the law and won. With Castro v. the Superior Court of Los Angeles, Acosta overturned felony conspiracy charges against teachers who walked out in protest of poor education in Latino districts. In the process, he speedballed himself into the political maelstrom. He nailed the L.A. County jury selection process for its discriminatory policies in Carlos Montez et. al. v. the Superior Court of Los Angeles County. He ran for sheriff of L.A. County. He represented the Biltmore Five, who were charged with arson for trying to burn down the Biltmore Hotel during a speech by then-California governor Ronald Reagan.

But alas, it was during the Biltmore trial that Acosta's Mr. Hyde caught up with his Dr. Jekyll. Busted for amphetamines by the LAPD, the leftist lawyer lost his La Raza clout overnight. He split for Mazatlan shortly after what Thompson would later characterize as a "high-speed drug bust." And the rest, as they say, is history.

Before he disappeared, the "three hundred pound Samoan" lawyer ensured his own sort of apotheosis. His books The Autobiography of a Brown Buffalo and Revolt of the Cockroach People were precedent-setting works. Pseudo-documentaries of California's Latino movement, they set the writer/attorney at the frontlines of literary Chicanismo. Ironically, after all Acosta's guerilla law tactics and his Jekyll-and-Hyde machinations, his books are now standard reading in Latino Studies programs around the country. And, of course, he was recently a central character (played by Benicio Del Toro) in Terry Gilliam's film adaptation of Hunter S. Thompson's Fear and Loathing in Las Vegas. Wherever he is, the Buffalo must be snorting with glee.

His son, Marco, recalls when his father met Thompson for the first time at the journalist's house outside Aspen in 1967. For the next several years, Marco observed the relationship that developed between the two -- the verbal sparring, the heated political exchanges, the inexplicable bond.

"They had a very interesting kind of spiritual connection, I think," Marco says. "They complemented each other in some strange way."

Perhaps it's best to invoke Thompson himself, who wrote a brutal, moving requiem to his friend in Rolling Stone in 1976. In "Fear and Loathing in the Graveyard of the Weird," Thompson cursed Acosta, maligned him, exonerated him:

"...I had never taken his burning bush trip very seriously -- and I still have moments of doubt about how seriously he took it himself… They are very long moments, sometimes; and as a matter of fact I think I feel one coming on right now… We should have castrated that brain-damaged thief! That shyster! That blasphemous freak! He was ugly and greasy and he still owes me thousands of dollars!"

The affection is unmistakable.

In the article's softer moments, Thompson revealed his true sadness when pondering the various Brown Buffalo sightings reported since Acosta's vanishing. The stories trickled in. "Ever since his alleged death/disappearance…he's turned up all over the world -- selling guns in Addis Ababa, buying orphans in Cambodia, smoking weed with Henry Kissinger in Acapulco…"

"It might even come to pass," Thompson added near the end of his eulogy, "that he will suddenly appear on my porch in Woody Creek on some moonless night when the peacocks are screeching with lust… Maybe so, and that is one ghost who will always be welcome in this house, even with a head full of acid and a chain of bull-maggots around his neck."

Shermakaye Bass is an Austin, Texas-based freelancer who covers arts, travel, and culture for newspapers and magazines nationwide.