It was after midnight in September 1982 and Patsy Wheat was exhausted and frantic. Neither 300 volunteers nor trained police bloodhounds had been able to find a trace of her missing 22-month-old son Jay after a day of searching in the Virginia mountains near Roanoke.

The Bedford County sheriff, however, was not ready to quit. He had heard about a search dog trained to track by a different method -- "It's called an air-scenting dog" -- and asked a Washington group to join the search.

Shortly after dawn, a German shepherd from Rockville arrived. Following the human scent carried by the wind, instead of a track left on the ground, the dog soon located Wheat's son on the top of a hill.

"I've always loved dogs," said Wheat, "but I loved them a whole lot more after that."

Virginia officials say that the specially trained dogs are proving increasingly helpful in a wide variety of operations, ranging from searches for missing children to searches for missing aircraft. "Their reputation is well known, and well deserved," said Paul Demm of Virginia's Department of Emergency Services.

"You cannot believe the nose that those animals have," said Bill Pierce, assistant chief ranger at the Shenandoah National Park.

Dogs-East, one of three such groups in Virginia, recently joined the massive Loudoun County search for Judith DeMaria, the tennis coach who disappeared while running along a popular jogging trail. Last week, a dog from the group took only four minutes to locate the victims of a small-plane crash in a thickly forested section of the Shenandoah National Park. More than 500 other searchers had been looking for the wreck for a week.

When Wheat's son disappeared three years ago, she had expected a team of animals and strapping woodsmen to show up at her house when the sheriff turned to Dogs-East for help. So when only the German shepherd, handled by a gray-haired woman, arrived on her doorstep that night, Wheat was disappointed.

"But when somebody in your family is lost, you'll try anything," she said. So, she sat down at her kitchen table while the woman, Marian Hardy of Rockville, unfolded maps and outlined her plans.

Hardy, 57, is Dogs-East's training director and unofficial manager.

Like the group's other 10 volunteers, she willingly descends into mountain ravines and forages down lonely roads in search of the region's lost and missing.

She likes to say that Dogs-East can be on the road within 15 minutes of a call, and she keeps a duffel bag at her home packed with three days' worth of clothes and dog food. "On the road" is a loose term, because Hardy is sometimes in a helicopter or huddled with her dog in the back of a rescue truck.

On the job, often in the middle of the night, she wears L.L. Bean boots (she wears out a pair a summer), a J.C. Penney uniform shirt, a helmet, a beeper and a walkie-talkie. She would like more equipment, but money has been a problem.

While Dogs-East volunteers are often fed and housed by those at a rescue scene (Hardy has eaten in jails and unrolled her sleeping bag in sheriffs' offices), the group's only cash has come from a few anonymous donors and Kal Kan Foods, a pet food company.

Members make up the difference. Hardy estimates that she gives as much as $5,000 a year from her federal retirement from the Defense Mapping Agency to help meet the group's $11,000 annual budget. "Our command post is a 27-foot mobile home, a Ford Condor," she said, "and that thing cost the earth."

Dogs-East always manages to respond, she says, with an assortment of dogs: a rottweiler, mastiff, standard schnauzer, bloodhound, golden retriever, yellow Labrador, Irish setter and German shepherd.

It takes about a year of intensive work to train a dog and handler, and the handlers say that the best of the air-scenting search dogs can detect humans buried in mud slides, collapsed buildings or snow.

When Hardy arrived in Bedford County, she told Wheat she wanted to search for the missing child before daybreak when people would begin moving about and the air would become filled with their scents. If an air-trained dog finds any human smell, it alerts its handler by sticking its nose in the air, Hardy explained.

It was 4:30 a.m. when the Wheats, Hardy and the dog edged along U.S. 460, and then along some railroad tracks. As they passed behind the Bedford Moose Lodge, about a half-mile from the Wheats' home, the dog's nose went up in the air.

Hardy told the Wheats that scent sinks to the earth at night, sometimes settling in spots blocked by the wind. She said Jay could still be in the area, maybe on higher ground.

Twenty minutes later they had climbed to the top of a 200-foot hill known as Moseley's Mountain. Then everything started to happen.

The dog's head jerked back as it sniffed the air, and it bounded about 100 yards down the backside of the hill. There was Jay Wheat, caught in briars, lying on the ground crying.

Hardy returned to Rockville at 10:30 p.m. on a recent night after searching for the victims of a small plane in Northern Virginia. At 2:30 a.m., her telephone rang. Two boys were missing on the Peaks of Otter near Roanoke. She grabbed her duffel, and set off into the night.

"You feel a real obligation," she said. "If you get a call, you must respond."