Roy and Teddy rescue Mr. Gregory, a man pinned under his horse, which has fallen and broken its neck. Since he was weakened by his ordeal, the boys take him to the X Bar X ranch to recover. There he reveals that he was bringing from his home in Denver to his recently widowed sister her title deed to a zinc mine. Her mine is one of three in close proximity to each other which together are called Triangle Mine. Unless she can prove her title by the first of the following month, her property will be taken over and she will be destitute. However, the deed was lost or stolen while the man was vulnerable, apparently by a traveling companion who has been proven false. Once he recovers his strength, the man takes off to track down the man responsible. Having business for their father in the vicinity of Triangle Mine, and being concerned about the welfare of their recent guest, the boys follow.

Writing: 8
Characterization: 6
Plot: 7
Overall score: 7