The Untamed by Max Brand

So when the first chill days of the late autumn came the four were once more together, Dan, Kate, Black Bart, and Satan. Buck and old Joe Cumberland made the background of their happiness. It was the latter's request which kept the wedding a matter of the indefinite future. He would assign no reason for his wish, but Kate guessed it.

All was not well, she knew. Day after day, as the autumn advanced, Dan went out with the wolf and the wild black stallion and ranged the hills alone. She did not ask him where or why, for she understood that to be alone was as necessary to him as sleep is to others. Yet she could not explain it all and the cold fear grew in her. Sometimes she surprised a look of infinite pity in the eyes of Buck or her father. Sometimes she found them whispering and nodding together. At last on an evening when the three sat before the fire in solemn silence and Dan was away, they knew not where, among the hills, she could bear it no longer.