It was the gaudiest, most expensive, most excessive spectacle ever filmed, a roller coaster through madness courtesy of Joseph Conrad, Francis Coppola and those wonderful guys who brought you the Vietnam war.

And it got to Martin Sheen from the outset of the filming of "Apocaplypse Now" in the Phillippines. . .all those nights turning into mornings, the smoke on the sets making him gag, the food that made him gag, too, the crew members dropping of heat exhaustion, the typhoon floods, the eternal changes of script, the amphetamine-like, Apocalypse-Forever exhaustion, the screams of his four kids who wanted to go home to their Malibu beach.

So the breakdown began, even as the military assassin he played started falling apart, nerves snapping like an M-16 on automatic. . .Sheen found himself screaming at his oldest kid, who called him a liar, battle-fatigued at work and at his mud hole called home. And finally, on March 5, 1977, Sheen collapsed from a heart attack.

Once again, the props of this epic film of martial madness turned into real life, with a Huey chopper lifting Sheen from the humid choke of the jungle to a hospital in Manila.

"I thought I was gonna die there," he says -- another American facing up to the haunting mortality of men who try to hustle Asia -- this time for the glory of the big screen.

One month later, Martin Sheen went back into the jungle to finish his journey.

Now, Martin Sheen seems stranded in some awkward DMZ between fame and obscurity.

It's a gray 8 a.m. in Middletown, Ohio, the first morning cold enough to turn words into white puffs of water vapor, and Sheen climbs out of his rented Hornet and hustles into McDonald's for some wakeup coffee.

This is home turf. Sheen was born in nearby Dayton 39 years ago, and now he's visiting for four days, in from Malibu to teach a drama workshop at the University of Dayton. Earlier this year his face was beamed into the homes of America for a full week, portraying John Dean in the TV docudrama "Blind Ambition," but his biggest acting effort, "Apocalypse Now," has yet to come to Ohio.

He's barely awake, but characteristically he's talking fast, asking the countergirl a few questions about salaries, since he's heard that, thanks to a quirk of the law, McDonald's employes can be paid less than the usual minimum wage.

"We get $2.90 an hour," she says. "It's real good pay and we still have a lot of openings."

And then, with all the sincerity of the Midwest, she says: "Look, mister, if you're looking for a job, I'll give you an application."

You can understand the question: Sheen, a ringer for James Dean, looks just like the rebel without a cause should in 1979: blue jeans, cowboy boots, tan flight jacket with a turned-up fur collar, and a wave of soft brown hair that he has to keep pushing away from his deep-set blue eyes. He sticks his hands in the pockets of his jacket.

He's a tough guy on the way to being a tough star, a Cagney for the '80's. He has a bitter-end charisma that has led him to play history's beautiful losers and Coppola's hired killer, but Sheen has his own hard side to tell:

"One night, in San Francisco, I tied one on and decided to take this restaurant apart, and my a-- wound up in jail. And I'm sitting there with this black woman, who's trying to get me to take some aspirin and apple juice for my hangover, thinking that I'm really in big trouble now, and I ask her what she's in for.

"And she says, 'I shot my fella.' Just like that: 'I shot my fella.'

"Now the irony of all this is that she probably should have shot that guy, because he treated her terribly, but she was going to get stuck in jail. And I -- the guy who took on the whole bar, the guy who should've been in jail -- I was going to get out because I had a good lawyer. Just like most of the justice handed out in this country: The Berrigan brothers do hard time for something they believe was morally right; and John Mitchell, how many days did he spend in jail?"

He dispels the tough-guy image quickly. His real concerns are with the woman in jail; the counter girl who's left her kids home to get up at 6 in the morning and sell Egg McMuffins for $2.90 an hour; all the guys who are laboring away in Dayton without union protection.

Those same sorts of social concerns led him to a weekend at the Kennedy compound in Hyannisport last summer; he was invited for the work he's done on the Special Olympics.

"I couldn't believe them as a family," he says, "especially Rose, who runs around like a drill sergeant barking orders. On Sunday everybody goes to mass. I could have been a devout Buddhist, and I would have had to go to mass. They get there just after the sermon, and park the car in the driveway, blocking the exit. And Rose says, 'Don't worry; we'll be out before everyone else.' And she goes to communion and then leaves, before everyone else.

"And then later we're all out on the sailboat, and Teddy is shouting orders like a real captain, and all the kids are doing exactly what he says.

"God, they love him. He's the only father figure they have, and he takes care of them.

"Jesus, I'm worried about him. I wish he could just drop out of this race. If he got killed, those kids would all go into shock. It's frightening."

But worries about that famous brother are not on Sheen's mind right now. He's concerned about his own brother John, who's bounced around from job to job, settling in as a disc jockey at WPFB-AM, a little podunk station in the middle of nowhere. John has only been there six months, and Sheen is up at dawn to make the long trek out to the radio station, to score a few points for his brother with the WPFB brass.

He's talking about Vietnam, John's bout with liquor over there, his own bouts with smoking and drinking, the problems of vets who were working on "Apocalypse," the doubts and fears of his own career.

"You know, I've never had a real success," he says in the car. After all the films and all the TV, all the rave notices and the great ratings, the high visibility roles of John Dean and Robert Kennedy ("The Missiles of October"), he's still a stranger to many of his hometown natives.

"I've never been in a blockbuster," he says. "I hope 'Apocalypse' will do it."

Underneath the hopes, you can sense a dose of frustration. He's annoyed with the critics who have trounced "Apocalypse," particularly a notice in Time magazine that called his work "reacting." He believes in the film, but has reservations about its editing. He thinks his performance is good, but worries about audience response to the mental slippage of his character.

Martin Sheen's involvement in "Apocalypse Now" roughly paralleled the production and dramatic action of the film itself: a mission turning into a nightmare. He had been working on another film in Rome, and flew to the Los Angeles airport for a 10-minute meeting with director Francis Coppola. A month later he began filming the Vietnam epic in the Philippines.

But the worst part of it all, he says, was a frightening confrontation with his then 14-year-old son Emilio:

"I'd been telling him for six months that we would be getting out of the jungle and going home -- I knew that we couldn't, really. And he finally called me a liar. He was furious. And this is not some little kid. He lifts weights, he could have whipped my a-- . We were screaming at each other, just about ready to go at it, when Marlon (Brando) strolled by. He'd heard all the noise. He was acting as if he was just walking by but I'm sure he came to make sure we didn't get in a fight."

For Martin Sheen, it was one of those incidents that forced everytning else into perspective.

"I realized for the first time after my fight with my son that it's really healthy when your kids can tell you that you're full of s-- -. The job of a parent is to take the responsibilities that the child won't or can't accept. My oldest son is my best friend now. We're going to work together in 'Mister Roberts' at Burt Reynolds' theater in Florida next February."

Now, driving along Interstate 70, he's singing an old Platters song:

Heavenly shades of night are falling

It's twilight time

Out of the mist your voice is calling . . .

He interrupts himself with another flashback from the Philippines, this one after his two oldest children had left to return home:

"We'd been shooting all night and the sun was just coming up and there was this mist hanging over the jungle and I'm being driven back to the house where I'm staying. The driver is playing an 8-track of that Platters song, and I'm saying to myself, 'I'm 36, listening to rock and roll, watching an orange sunrise in a strange country and my children are in America. What the f... am I doing here'?"

He's driving through Dayton now, past the National Cash Register building, where all his brothers have worked, where his father worked, remembering, "I used to think that building was so big. They used to show movies there for the kids of employes, and they'd have a Christmas party every year. Once they gave each of us a silver dollar, and I kept that big, beautiful dollar for years and years. I used to think that company was so wonderful. Now I realize that those bastards wouldn't let a union in there for years."

In Dayton at the drama workshop, Sheen is no Hollywood hotshot helping the kids; just an indulgent big brother, letting Bob run through the Grand Inquisitor's speech from Shaw's "St. Joan" and Lee recite "To Be or Not To Be."

"The whole motive of acting," he tells them, "is to not be acting; just thinking. What I find interesting is the road we have to travel to get where we're going. Acting is doing publicly what everyone else does in private. That's what an audience responds to. And when anybody's up there in front of an audience, there's a little piece of all of us up there."

The kids are flabbergasted: a blood-and-guts star, treating them like they have something real to offer. They respond with enthusiasm, only occasionally driving into fandom, popping instamatics and asking for autographs.

Sheen knows how to work with big groups of kids. He grew up with eight brothers and one sister in a working-class neighborhood, trekking off every morning to serve mass at Holy Trinity Church. His father was born in Spain and emigrated to Cuba, where he became a repairman for NCR. The company sent him to work in its foundry in Dayton, where he married an Irish woman and raised a family, including Ramon Estevez -- still Sheen's legal name. His first play was in sixth grade, "The Ax in the Forest."

Sheen's mother died when he was 11. His father raised him, and insisted that he attend college, even though Sheen was set on acting. So he gave his first great performance, flunking the U. of D. entrance exam on purpose, scoring a record low of 3 out of a possible 100.

"You know," he says, "I'm really stupid. I can't spell. I get a bill and I can't figure out what the hell it means. But I always knew what I wanted to do. I used to sit in my senior year of high school and watch the B&O trains go by and I really wanted to jump one of those suckers and head for New York."

After graduation, he left his girl friend Barbara behind and hopped the Greyhound headed for the Big City where he changed his name: Martin, because that was his only friend in New York, and Sheen, he says, "because as much as anything else at that time I really admired Bishop Sheen, and it seemed to fit with Martin."

Within a few years he had joined Julian Beck's political living Theater and first met his wife of 18 years at a beer party. By the mid-60s he was ensconced in a Broadway smash, "The Subject Was Roses." After several TV jobs, he left New York in 1969, "on the day the Jets beat Baltimore in the Super Bowl," and flew to Mexico for a role in "Catch-22." He fell in love there with warm weather and moved to Southern California. Since then Sheen has played several memorable roles: the Charlie Starkweather character in "Badlands," his favorite performance, one that came in 1972 opposite the then-unknown Sissy Spacek; Robert Kennedy in "The Missiles of October"; the young hero of "The Execution of Private Slovik"; and John Dean in "Blind Ambition."

He's finally at the station, on the air, talking about the 50s and Chuck Berry and Sal Mineo and the Platters and James Dean. Next year, on the 30th of September, he'll be in Fairmount, Ind., to mark the 25th anniversary of Dean's death. "I was asked to play him, but you can't play James Dean; he played himself." He'll be on "Saturday Night Live" next month, possibly with Bob Dylan. "Dylan lives around the street from us in Malibu. Our children are friendly but I never met him." He's got two new films finished, and is considering a role as jazzman Bix Beiderbecke or Jimmy Cagney.

It's time for a commerical, and Sheen begins to read through the copy, blowing it seven times before he gets it right: "There are loaves of fresh bread baked rising in the Central Pastry ovens. Central Pastry, 1518 Central Ave., has their bakers quite busy hand-crafting 11 different types of breads. . ."

A few minutes later the station ad manager walks in the studio. They're lining up down at Central Pastry, she says, and the bakery has committed to several more weeks of ads -- if Sheen will read the copy.