The Mystery of Ghost Canyon by Dan Scott

Hardcover. Condition: Fine, Dust Jacket: Good. 1960. Grosset and Dunlap.

Book #1 in the Bret King Mystery series. It's serious business when Rimrock Ranch loses cattle to rustlers. Bret King and his pals Ace Tallchief, Andy Buxton, and Benny Ortega saddle up to trail the culprits. A few tire tracks and a steer hide are the only clues.
Meanwhile, Benny's parents earn some extra money by renting their property to Professor Colfax and Dr. Dudley, who plan to search for artifacts in nearby Oro Perdido Canyon. The scientists act mighty peculiar, warning the cowboys to stay away—or else! Why do the scientists act like desperate outlaws?

A mysterious plane is spotted in the area and lands near Oro Perdido Canyon. Strangely, the occupants refuse to speak to the boys and seem to be affiliated with the hostile scientists. Could these events have any connection to the cattle rustling?