SUMMERTIME IS UPON US, AND THE siren song of the open road is calling Americas motorists. After they find out what happened to Fred and Jeanne Howard, though, they may think twice about even pulling out of their driveways.

The Howards' misadventures began last July as they were tooling along Highway 55 in Idaho. Intrepid RV-ers, they were on their way back home to Lake Ariel, Pa., towing their 1982 Honda Civic behind their 1987 Fleetwood Bounder. Thirty miles north of Boise, Idaho, the car's right-rear lire blew.

Fred drove on, unaware of the blowout—or of the pieces of burning rubber the Honda was spewing onto the dry grass along the highway. Sure, drivers were honking their horns at him and blinking their headlights, but Fred is used to that. "When you're holding up traffic in a big RV," he says, "people honk and blink their lights all the time."

Finally, Fred spotted flames in his rear-view mirror. He pulled over and unhitched the burning Honda. That's when he saw the rising plume of smoke that marked his progress—a fire that would eventually scorch 6.258 acres and take 700 firefighters to control. "I felt bad," says Fred, 67, a retired Air Force quality-control engineer.

He would soon feel much worse. After they returned home, he and Jeanne, 70, received a bill from the slate of Idaho for firefighting services: $1,013,500.10. "We were stunned," says Jeanne. "The only part we can afford is the 10 cents."

Idaho, for its part, is dead serious about trying to collect from the Howards, who live on Fred's $1,700-a-month pension plus Social Security. A civil trial is set for October. "It's state law to bill people we know are responsible for forest fires," says Winston Wiggins, an official of the state Department of Lands. Wiggins did concede that if a fire is started by, say, lightning, "we certainly wouldn't send a bill to God."

For mere mortals who plan to visit Idaho, though, the lessons are clear. Only you can prevent forest fires. And only you can be billed for them.