A MOST EXCELLENT ENIGMA

Natasha Stoynoff in Toronto and Karen Brailsford and Kristina Johnson in Los Angeles

A walking mystery with a foggy history, Keanu Reeves has a hit with Speed. If you knew Keanu . . . you'd be rare

AT 29, ACTOR KEANU REEVES HAS worked with great directors (Francis Ford Coppola in 1992's Bram Stoker's Dracula), done Shakespeare (last year's Much Ado About Nothing) and starred in a certified summertime smash, the current hit Speed. A pleasingly mindless action romp in which Reeves plays a S.W.A.T. officer battling a mad bomber, the film has grossed more than $60 million since its release four weeks ago. It has also established the romantically unattached Reeves as a true heartthrob and a mainstream star. About the only thing it hasn't done, in fact, is make him overtly cheerful. "There's a hint of sadness in his eyes," said Sandra Bullock, his love interest in Speed. "It makes you want to go, 'What is it?'"

Whatever the source of Reeves's melancholy, it has made him his own man -- a kind of mellow rebel in a town that wouldn't mind if he stepped up to the challenge and became the Arnold Schwarzenegger of the slacker set. "I don't have any ambition to do that," Reeves has said. "I don't want to be superfamous, man. That would be awful."

Reeves seems to let nothing -- including the fact that he already is famous -- interfere with his assiduously offbeat existence. He lives, for example, out of a suitcase in a room at the celebrity favorite Chateau Marmont hotel on Sunset Boulevard. For fun he rides his Norton Commando motorcycle. Nothing too odd there, except that Reeves once particularly enjoyed the occasional late-night cruise with the headlight turned off. "I've gotten many tickets," Reeves admitted. He also has a scar on his abdomen from a serious motorcycle accident he had about seven years ago.

"He's the archetypal troubled young American," says John Malkovich, who worked with Reeves on 1988's Dangerous Liaisons. "He's like your younger brother, someone you should be helping out in some way. He doesn't invite it. I don't think he would like it much. But if you're older, you feel you should protect him."

It's an understandable instinct; Reeves has had anything but a charmed life. His father, Samuel Nowlin Reeves, a geologist of Hawaiian-Chinese descent, left the family when Keanu (the name means "cool breeze over the mountains") was a child. The elder Reeves, who hasn't communicated with his children in more than a decade, dropped out of sight for years, only to reemerge as a convicted criminal; just last week he was sentenced by a Hilo, Hawaii court to 10 years in prison for cocaine possession. Keanu and his two sisters, Kim, now in her mid-20s, a part-time model, and Karina, 18, a recent high school graduate, were raised in Toronto by their mother, Patricia, a British-born designer of theatrical costumes. Theirs was a life long on love beads, incense and visits from clients of Patricia such as Alice Cooper -- but short on discipline. "I don't think he was ever on time for any lesson," says Paula Warder, a teacher at Jesse Ketchum grade school, which Reeves attended in Toronto. But when he did show up, she adds, "he had a smile on his face." Always a restless student, Reeves switched high schools four times before dropping out in 1984. Two years later, having dabbled without much success in local theater, he hopped in his 1969 Volvo and headed for Hollywood.

The movie industry provided Reeves with acceptance, freedom -- and a soulmate in the person of River Phoenix. The two -- both the products of bohemian upbringings far from the film studios -- met while shooting Parenthood in 1989. By the time they were costarring as perennially stoned street hustlers in My Own Private Idaho in 1991, Phoenix looked to Reeves, six years his senior, as "an older brother," he has said. Rumors of drug use dogged the two, and in the case of Phoenix, who died of an overdose last October, proved all too true. Reeves, though he refuses comment on the subject now, has in the past expressed a fascination with drugs. "I want to be on speed!" he told Interview magazine in 1990. "I've never been on speed. I want to be a speed freak for a while. Is that a stupid thing to say?" Still, Jan De Bont, the director of Speed, has said that Phoenix's sudden death "scared the hell out of" Reeves.

In Speed, Reeves certainly looks like a healthy specimen. At the request of De Bont, he cut off the scraggly mane that has been his trademark since 1989's Bill and Ted's Excellent Adventure. He also pumped iron for two months at Gold's Gym in L.A. to add manly umpf to his formerly lanky frame. Not that Reeves is on the verge of becoming an entirely sensible adult. He is still likely to break off a polite conversation and suddenly start talking to himself. He could easily be voted Least Likely to Maintain a Serious Romantic Relationship -- quite a distinction among young male movie stars. And he still likes to surf, play his guitar very loudly and ride his motorcycle way too fast. "Time goes much slower when you're moving at around 130 mph," he once said. Oh, well. This is Keanu's moment, and he is savoring it in his fashion.