At the wheel of her Dodge Durango, Tammy Gordon rounded a bend in rural Hawthorne Road, not far from her Charles County home, and suddenly braked.

Fear crept over her as she stared through the windshield. Down a slope in the road ahead, she saw a cluster of police cars, their emergency lights flashing.

A crash site. Yet as she edged toward it, she saw no wreckage.

She had been driving for about 10 minutes last Saturday, searching for her husband, Steven Gordon, 38, who was late getting home from an afternoon bicycle ride.

She thought about lowering a window to ask an officer if a bicyclist had been involved -- but she couldn't bring herself to do it. Instead, she tried not to worry.

"I'm going to find him," she later recalled thinking. Most likely he had a mechanical problem and nothing more. "He's further along -- he's walking along, carrying the bike." She told herself they would "end up laughing about it."

Her husband, an avid fan of the Tour de France, had begun riding seriously about 15 years ago, well before Lance Armstrong inspired countless people to take up cycling. He and a friend were looking forward to a September trip to France, where they planned to cycle up mountain peaks -- the Mont Ventoux, the Col du Galibier and the Alpe d'Huez -- where some of the Tour's most exciting moments have occurred over the years.

He had been gone on his bike nearly four hours when Tammy Gordon, 38, came upon the police cars near Indian Head Peninsula in the northwest part of the county. His body had been removed by then, and the motorist who hit him had been taken away in handcuffs after police allegedly found marijuana in his car.

She eased the Durango by the burning flares stuck in the pavement, saying nothing to the Maryland state troopers.

"I wanted to keep looking," she said.

When America began its love affair with the automobile generations ago, the idea of an adult on a bicycle grew increasingly foreign -- literally. While thousands of adults bicycled through the streets of Paris, Beijing and other cities around the globe, by the 1950s cycling was generally seen in the United States as child's play.

That notion has been turned on its head over the past 25 years, driven by an increasing desire for adult fitness and helped along by attention paid when a pair of Americans -- Greg LeMond and Armstrong -- triumphed repeatedly in the world's most famous bike race, the Tour de France.

At bike shops, sales of adult-size bikes have surpassed those of kiddie bikes, and charity rides, bike clubs and regular group rides have made the sight of adults pedaling on the roadway commonplace.

The number of adult deaths was bound to climb, too. A U.S. Department of Transportation study found that adult bike deaths tripled from 1975 to 2000, while deaths among children 15 and younger dropped by two-thirds, in part because of new helmet laws.

Bike sales were projected to total $5.3 billion last year, and a growing sliver of that market belongs to road bikes, the light, sleek racing machines ridden by Armstrong and his foes as the three-week Tour de France nears its finish tomorrow. Sales of those bikes have risen dramatically in just the past two years, according to the National Bicycle Dealers Association, at an average price of $1,152 last year.

Gordon set out on his road bike about 11:30 a.m. Saturday after a relaxing morning at home.

He got up early, ate a bowl of bran cereal, then went to a bedroom to watch the Tour de France on TV. His wife and 8-year-old son, Tommy, were loafing in the living room, watching another program. The couple's daughter, Jessie, 12, and some friends who had slept over had control of the basement.

Gordon had been following the Tour religiously, taping the televised stages on weekdays and watching them at night. Only on weekends did he have time to watch live coverage.

This year's Tour had special significance for Gordon, the head of magnetic resonance imaging at Fairfax Radiological Consultants. He and a colleague, Lyn Goodwin, planned an eight-day cycling trip in France. They had their tickets: On Sept. 10, they were to fly to France and stay in Bourg d'Oisans, a village in the Alps. From there, they would set out to ride some of the famous mountain peaks of the Tour.

These are grueling climbs that challenge the world's best cyclists, including Armstrong. Last year, after they watched Armstrong sprint up the Alpe d'Huez in a time trial, Gordon and Goodwin decided they would try it, too.

Gordon rode a bike built by Trek, the company that supplies Armstrong's bikes. He and Goodwin had put in lots of miles together, including a multiple-day tour through Virginia. Gordon rode "strong and fast" without saying much, said Goodwin, who called his friend "a rock-solid guy."

Through the spring and into summer, Gordon trained. He rode in the Blue Ridge Mountains to get his body in climbing shape. He lost 14 of the 20 pounds that he wanted to shed and tinkered with his bike to make it lighter.

Saturday, after watching the Tour on TV, he emerged from the bedroom in his cycling gear, pumped up and ready to ride. He mixed energy powder with his orange Gatorade, grabbed his helmet, a spare inner tube and tools, and off he went.

Less than an hour later, he was pedaling northwest on Hawthorne Road, a favorite route. Unlike a lot of rural roads, Hawthorne has an ample, eight-foot-wide shoulder marked by a solid white line. It is big enough for three cyclists to ride shoulder to shoulder.

A blanket of humidity hung over the Washington area as temperatures hovered around 90 degrees. As Hawthorne Road heads northwest toward the Potomac River, the smooth, gray macadam stretches flat for a few miles. Gordon could have traveled fast enough to hear wind whistling. Then, after a bend, the road descends. On the downslope -- in the seconds before he died -- Gordon easily could have reached 30 mph.

Police said a Mitsubishi Eclipse traveling at an undetermined speed swerved onto the shoulder behind Gordon and struck him -- not a sideswipe, but a direct hit, which dented the center of the Mitsubishi's front license plate.

The impact hurled Gordon into the air, and he came down on top of the car as it stopped, shattering its windshield and caving in the roof, police said. Then he tumbled to the pavement with massive injuries.

He was buried Thursday after a funeral at First Baptist Church of Waldorf.

When Trooper Leonard K. Hewitt arrived at the crash scene about 12:15 p.m., minutes after the crash, he saw the mangled bike on the ground about 10 feet from Gordon's body. The driver of the gray Mitsubishi, Don S. Pittman Jr., 30, was sitting on a guardrail, in short pants and a yellow jersey.

"He appeared to be in a daze," Hewitt wrote in an affidavit filed in court. "I suspected he was under the influence of a drug and/or alcohol."

Pittman, who lives in the county's Pomfret area, had gone out for fast food and was on his way home when the crash occurred, police said. He did not respond to telephone messages from a reporter this week seeking his account of what happened. According to the affidavit, he told Hewitt that he had smoked marijuana the night before and had taken a dose of Zyban, an antidepressant, about 90 minutes before the crash.

Searching the 2003 Mitsubishi, Hewitt wrote, he found a Budweiser bottle on the floor and a baggie under a seat containing 6.5 grams of marijuana.

At the state police barracks in La Plata, Hewitt gave Pittman three sobriety tests.

When the trooper held up a finger and moved it from side to side, asking Pittman to follow it with his eyes, Pittman could not smoothly do so, Hewitt said in the affidavit. He said Pittman was unable to smoothly walk nine steps, heel to toe, and could not stand with one foot six inches off the ground while counting to 30.

Pittman was charged with possessing marijuana and released from the county jail early Sunday on $5,000 bond, according to court records. Hewitt said in the affidavit that "further charges are pending" while authorities await the results of a blood test on Pittman and a report by the state police accident investigation unit.

After she passed the crash scene, Tammy Gordon called her daughter. "Has Daddy got home yet?" she asked. No, said Jessie. And he hadn't called.

Maybe she had just missed him, she thought. Maybe he was up ahead. She kept driving, along lonely roads, past farms and new subdivisions, hoping to see him.

Finally, she drove home.

And she waited.

And then she got out a phone book and called the county sheriff.

"Were there any accidents involving cyclists today?" she asked.

When the sheriff's office transferred her to the state police, she inquired again: "Have there been any accidents involving cyclists today?" The call-taker said yes and began asking her questions about her husband. And now the fear that had crept over her took firm hold, and there was no escaping it, no way to block it out.

"And then it became hard to breathe," she said.

Ashes from police flares mark the area on Hawthorne Road in Charles County where Steven Gordon was struck and killed while on an afternoon bike ride.Steven Gordon was a serious cyclist.Don S. Pittman Jr.'s car struck Gordon.