The Spirit of the Border by Zane Grey — Read

The sight which Joe had seen horrified him, for several moments, into helpless inaction. He lay breathing heavily, impotent, in an awful rage. As he remained there stunned by the shock, he gazed up through the open space in the leaves, trying to still his fury, to realize the situation, to make no hasty move. The soft blue of the sky, the fleecy clouds drifting eastward, the fluttering leaves and the twittering birds -- all assured him he was wide awake. He had found Girty's den where so many white women had been hidden, to see friends and home no more. He had seen the renegade sleeping, calmly sleeping like any other man. How could the wretch sleep! He had seen Kate. It had been the sight of her that had paralyzed him. To make a certainty of his fears, he again raised himself to peep into the hole. As he did so a faint cry came from within.

Girty lay on a buffalo robe near a barred door. Beyond him sat Kate, huddled in one corner of the cabin. A long buckskin thong was knotted round her waist, and tied to a log. Her hair was matted and tangled, and on her face and arms were many discolored bruises. Worse still, in her plaintive moaning, in the meaningless movement of her head, in her vacant expression, was proof that her mind had gone. She was mad. Even as an agonizing pity came over Joe, to be followed by the surging fire of rage, blazing up in his breast, he could not but thank God that she was mad! It was merciful that Kate was no longer conscious of her suffering.