Treve, a beautiful and madly-alive collie, must fight for his life after his owner mistreats and rejects him. Through a series of unfortunate events he finds himself on the Dos Hermanos sheep ranch, and the two owners of that ranch become his new masters. Treve immediately loves and is loved by Royce Mack, the younger of the two ranchers, but Joel Fenno, an embittered, cranky old rancher, takes an instant dislike to Treve. He has "no time for measly pets and the like" and shows his contempt for the faithful sheepdog as often as he can. While the brave collie is protecting sheep, saving the ranchers' lives, being kidnapped by his previous owner, and many other harrowing adventures, his loyalty and love is also turning the heart of a bitter old man.