Jo Rinehart arrived at her parents' home and knew the empty driveway and locked house were bad signs. When she went inside, she saw that her mother's cellphone had been forgotten on a kitchen counter. It was filled with worried, frantic and plaintive messages from Rinehart and her siblings, all left in the previous 12 hours.

"Did you make it home?"

"Where are you?"

"Call us."

"We're coming to your house."

Rinehart's parents, William Fresch, 85, and his wife, Betty, 79, had not been seen or heard from since about 5:15 p.m. Friday, when they left Rinehart's home in Mechanicsburg, Pa., for what was usually a 40-minute drive back to their house in Shippensburg, Pa., 25 miles north of the Maryland border.

The grown children had brokered a deal that might sound all too familiar to adult children trying to protect - and yet, respect - aging parents. The Fresches could keep their car, but drive only to Rinehart's home or around Shippensburg, and only if they called to say they had made it back home safely.

It was a trade-off, but one that seemed to have worked over the past couple of years, Rinehart said.

After she didn't find her parents at their house, Rinehart, 54, and her husband called police, who put out a regional alert for the couple. Rinehart and her husband talked to reporters, posted her parents' pictures on Facebook and searched roadways themselves, even going up in a private helicopter Tuesday to scour the area.

By 11 a.m. Tuesday, their wait was over,

Her parents' bodies had been found. Authorities think William and Betty froze to death in a steep farm field off rural Gene Hemp Road in Frederick County, Md.

A passerby who had spotted the couple's red Honda Accord, stuck in a field with a deep pitch and a ravine, tracked footprints and found the bodies a few hundred yards away from the road, said Cpl. Jennifer Bailey, a spokeswoman for the Frederick County Sheriff's Department.