Fleeing from murderous Apaches, Bo Logan finds a hidden valley in the Arizona desert but he also discovers a mystery that he can't ignore. Tom O"shay, a miner, has a cabin in the valley but he has vanished and his young daughter Bonnie is stranded somewhere in the slums of New York City. Bo must choose between courting Mary, his new found love in Tucson or traveling across the country and undertaking the almost impossible task of finding young Bonnie. Will the treasure at Rainbow's end be found?