When ex-deputy US marshal Jack Tracy returns to the Box T Ranch in Colorado after a lengthy absence, he arrives just after his parents and brother have been murdered by the infamous Laredo gang. Starting out on a long and perilous endeavour to bring the gang to justice he is joined by Ruth Mailer, whose father was also murdered by the gang during a stagecoach robbery. As they follow the gang through Colorado, the Texas Panhandle and the Indian Territory, they constantly face the risk of death at the hands of the gang and their criminal acquaintances. Working mostly on their own, can they possibly survive long enough to complete their task?