A hiker missing in Olympic National Park since Tuesday is alive and in good condition after walking out on her own Saturday. Mary O'Brien, 45, an...

A hiker missing in Olympic National Park since Tuesday is alive and in good condition after walking out on her own Saturday.

Mary O’Brien, 45, an experienced hiker from Arlington, Mass., was rescued after finding a person in a motorboat at Lake Mills and using a cellphone to call 911.

She had walked about 20 miles out of her way after she veered off the 18.5-mile High Divide loop trail in the Sol Duc River area during a day hike Monday, park spokeswoman Jacilee Wray said.

When O’Brien didn’t show up to meet friends in Seattle on Tuesday night, the park began a search along with the Washington State Patrol and a Thurston County sheriff’s Whitewater Rescue Team.

Because of snow on the ground, O’Brien had missed the return route on the High Divide trail down to Sol Duc Hot Springs and over the week hiked through Cat Basin and up and down Mount Fitzhenry before reaching Lake Mills, Wray said.

O’Brien didn’t have a sleeping bag or a tent but managed to sleep during her ordeal. She also had enough food to last the first three days.

“She’s a hearty hiker,” Wray said.

O’Brien was being debriefed by Olympic National Park staff members Saturday evening and could not be reached for comment.

Kirsten Orsini-Meinhard: 425-745-7807 or kmeinhard@seattletimes.com