The Rainbow Trail.

John Shefford is looking for his uncle Venters who years ago found a hidden valley and lived there with Jane Withersteen and young Fay Larkin. He finds Kay, now grown, who tells John that Willets and his men got into the nearly inaccessible valley and she has agreed to marry him to save the lives of the other two. John and Fay head for the valley with Willets and with his men right behind.