Under the damp, pink, flowering trees she comes running, grazing the pavement, arms held loosely, legs working quick and light in the March Oregon chill. Brown curls hang around her forehead. Her orange sweatshirt is moist from the morning drizzle.

She lets herself into the house. She turns on the "Today" show. She lies on the carpet to stretch, pulls softly where the calves ache, where the surgical scars had begun to throb.

She is 21 years old, big-eyed, skinny, and the fastest female miler in the world.

Legs over head, stretching.

Where does she keep the trophies?

"In boxes." Her voice is muffled in the stretch. "Hidden."

Legs doubled back underneath her, stretching.

How many are there?

"Plenty."

Situps, hands folded over stomach.

"The thing is --" situp -- "they're so useless." Situp. "They look kind of ugly, too --" situp -- "all this metal sitting around."

Eight weeks ago, before a crowd of 25,000 people in Auckland, New Zealand, Mary Decker ran the mile in 4:21.7, which set a world outdoor record.

Six weeks ago, in Madison Square Garden, at a meet that suddenly turned into a cheering madhouse when the crowd saw what Decker was doing, she ran 1,500 meters in 4:00.8, which broke the world indoor record by two full seconds and the American indoor record by nine.

Five weeks ago, in the Houston Astrodome, she ran the mile in 4:17.55, shaving three seconds off her own record.

Four weeks ago, in San Diego, she ran 880 yards in 1:59.7, which shattered the two-minute women's mile-stone. Mary Decker set her fourth world record in a year that has hardly had time to get under way.

The prodigy, ladies and gentlemen, is back.

In a sport where full strength and speed generally come during the mid-to late 20s, Mary Decker was a world-ranked half miler when she was 14 years old.By 15, she had set three indoor world records, traveled three continents in international competition, and received a bronze sculpture from the premier of Senegal.

By 16, as far as track was concerned, she was practically a cripple.

Four years ago, with each running step a private agony of leg cramp and muscle pain, Decker had dropped so far from competition that a good day was the kind where she made it through a slow half-mile without crying. She had stress fractures. She had constricted muscles. She had Achilles tendinitis, and back pain, and -- after a jovial tussle with a friend that left Decker flat on her back on a wet sidewalk -- whiplash.

The tut-tuts crooned in chorus: burnt-out, has-been, bright new light gone dark so young. Decker ignored them all.

"I know that athletes get injured," Decker said lightly, voice as high and clear as a young soprano. "I'd just think, 'Well, these sorts of things can't go on forever.'"

The word "comeback" seems a little silly here. Mary Decker has roared back into middle-distance competition, running with such speed, such pacing, such strength and control that nearly every major 1980 race she has entered has turned into a raw contest between Decker and the clock.

At the Millrose Games in Madison Square Garden, she lunged ahead of the other 1,500-meter runners and tore around the small indoor track in a first-quarter time that had the announcer as excited as the crowd: "Officially, 60.3," he cried over the loudspeaker. "Not even Eamonn Coghlan --" world record holder in the men's indoor mile -- "ran that fast."

Easing up now, a piddling 80 miles per week or so, Decker is poised at the crest of her greatest season. Here in this rain-cool runner's town, where track athletes gather like pilgrims and the legacy of the late middle-distance genius Steve Prefontained still lays some steady inspiration along the footpaths, Decker lives within the benevolent embrace of the Nike shoe company, which employs her around three hours a day to sell shoes in Eugene.

She has grown into a slender, restless, engaging young woman -- not at all athletic-looking when she changes out of her track clothes.

She wears a tiny gold chain with a heart on it, which she fingers when she is nervous, and dusky shadow over her large brown eyes.

She shares a sparsely furnished house with two other athletes. Her giggle turns heads 20 feet away when it explodes out of control.

She signs autographs gracefully, but the veteran's veneer is not thick. On the second round of wine in a restaurant in Portland, when her friends merrily tell the waiter who she is ("Did you see the cover of Sports Illustrated?"), Decker covers her face with both carefully manicured hands and shrinks into her corner of the booth, cringing and giggling.

And all around Mary Decker, knowing just how far she will push herself to get what she wants, friends and coaches hover and watch and try, as the Nike-sponsored team coach said, to "keep her in harness, more than anything else."

A chiropractor works on her back twice a month. A team physiologist takes samples of her blood every Monday, checking for abnormalities that might indicate illness or stress. Tacked to the wall of her bedroom is a note from her New Zealand-based coach and boyfriend, Dick Quax, who met Decker when she was close to despair over the fierce stubborn pain in her legs. "If you don't take it easy," reads the stern handwriting on the note, "I will kick your butt."

Decker ran because she was bored. This is a famous story among runners by now.She was 11 years old, hanging around and bored in, Huntington Beach, Calif., and she and a friend saw a flyer for a parks department cross-country race.

Decker was not sure what cross-country meant. She just went out there and ran it and won -- "by a long ways," she told an interviewer a few years ago. "I don't remember it's being very hard."

A coach spotted her in a race not long after that, and Decker began to work -- racing and training so fast and so far that people who knew her grew anxious. When she was 12, she ran a marathon one day, 440 and 880 races the next. She won the Pan-Pacific Games when she was 14.

She was corresponding with Steve Prefontaine, and in his letters he repeated what he told a magazine writer in 1974: "Her future could go up in smoke if she's pushed too hard. I counldn't believe her training schedule. She could become so sick of running that she'll want to retire at 18."

The press popped her into that special slot -- the one reserved of Olga Korbut and Tracy Austin and the other charming little teen-agers whose innocence is as interesting as their achievements.

It was duly reported that Decker wore braces, plucked her eyebrows, wept after a rough encounter with a Soviet runner during a relay and cried when the premier of Senegal sent emissaries bearing honorary sculpture.

There were references to the great Jim Ryun, who ran his first sub-four-minute mile at the age of 17.

Her coach, who was catching a lot of flak for overrunning his extraordinary pupil, kept waving aside the fretful: Decker, he insisted, simply loved to run. And although she did finally change coaches, Decker would back him up. "I always said, 'Oh, I'm not going to burn out,'" she says now. "How do you burn out? You don't physically burn out. You go to sleep, your body repairs itself, you rest . . . it's not like a flame dying and being gone."

She was great; she was bubbly; she was headed for Montreal.

Then the pain began.

She felt it the first time on a training run, in 1974, near her home. It started in her ankle. She had X-rays but they didn't show anything wrong, so she flew to Japan for competition. She missed three of her four races. She was X-rayed again, and this time they found it: stress fractures, tiny cracks in the bone.

Decker was in a cast for six weeks. The cast came off, she started running, and the pain came back. It moved up into her calves. She was told it was shin splints, which is a catch-all phrase for trouble in the muscles along the calves; Decker was frantic for treatment that would work.

She packed ice around her muscles.She took cortisone shots and antiinflammatory drugs. She had acupuncture and acupressure and non of it worked, nothing kept the pain from gripping each bare calf as Decker struggled through her runs.

"The most frustrating part was, you'd go to see someone, and you'd get your hopes up," she said. "You'd think, 'Well this is really going to work.' And then it would fall through."

The Olympics a hollow joke by then, Decker moved to Boulder, where a clique of nationally ranked runners gravitated around the veteran Frank Shorter's sporting goods outfit. Running in pain and "on guts along," as one coach said, Decker entered a college competition -- she won the 440 and placed third in the 880 -- but the intense racing had completely stopped.

When a Denver doctor found more stress fractures up and down Decker's shin bones, she was put in leg casts for 12 weeks straight.

A week after the cast came off, the pain was back.

Decker painted, sketched, rode bicycles, walked a lot, enrolled in the University of Colorado, tried to keep busy enough to ward off despair. She had grown up around runners. Almost every friend she had was a runner. "I never honestly can say that I gave in," she said.

Quax gave Decker back her legs.

On a visit to Boulder from his home in Auckland, New Zealand, Quax listened intently to the details of Decker's pain. He had gone through precisely the same thing. Quax is a world-class middled-distance runner and in his frustration he had finally undergone surgery -- which cured the pain.

It was a relatively simple procedure, but rare in this country in 1977. Decker's calf muscles along the outside of her legs, her orthopedic surgeon explained, had grown too large for the fibrous tissue sheaths that encased them. If the surgeon slit the sheaths, he could open up two more inches in each calf, and the sheaths would eventually repair themselves to accommodate the new size.

Decker had the surgery. "I thought, 'What the heck, I have nothing to lose,'" she said. Two weeks afterwards, moving carefully along soft grass, she tried her first slow run.

The pain was gone.

There was aching in the scars, but Decker knew right away that this was not the old pain. "I couldn't believe it," she said, still sounding delighted.

The training started in earnest again. She developed Achilles tendinitis, but she rested and got better. She had the fall that gave her whiplash, but she eased up and took care of that. She felt something dimly like the preoperation calf pain, learned that the same procedure could be performed on her inside calf muscles, and went straight to the surgeon. He suggested she wait a month to see if the pain eased.

"I said, 'You guys, I don't have time to wait. Please do the surgery.'"

Propelled now by the approving roar of track audiences from Auckland to San Diego -- "The crowd just won't let you stop," she said -- Decker runs in her new home town with the Nike-sponsored Athletics West track team. Of 29 national and world-class athletes, she is the only woman..

"She is the toughest trainer we've got," said Harry Johnson, the team coach. "And that really isn't a slam on the rest of the guys. It's just a compliment to her."

But what else is left, Johnson is asked, for a woman barely out of her teen years who has gobbled up world records on the average of one per month?

"She doesn't have that little round gold thing," Johnsons said, making a precise O with his thumb and forefinger. "And thanks to our illustrious leader, won't have a chance to get it. I think she's one of the people that probably really has a gripe."

Mary Decker wants to go to the Olympics, She wants that more than anything right not, partly because every athlete wants the little round gold thing, and partly because she is now so fast that her only real competitors are the Eastern Europeans she would encounter at Moscow.

She loves a great tactical race, the kind where the clincher is knowing which furious pacer has no strong sprint -- so you can breathe down her neck unitl you kick out at the end to win it -- and who in the lineup is trying to do the same thing to you.

"There just wasn't any competition," Decker said sadly," remembering the New Zealand world record race. "I came back here looking for competition and there wasn't any either." She stifled a yawn.

In her dreams, when she runs, she is running alone, pacing faster and faster, her legs free from pain. She wakes without crossing the finish line.