That thundering pace soon brought Helen's horse to the timber.

Here it took all her strength to check his headlong flight over deadfalls and between small jack-pines.

Helen lost sight of Bo, and she realized it would take all her wits to keep from getting lost.

She had to follow the trail, and in some places it was hard to see from horseback.
Besides, her horse was mettlesome, thoroughly aroused, and he wanted a free rein and his own way.

Helen tried that, only to lose the trail and to get sundry knocks from trees and branches.