Death Rides the Range (1939)
This film finds Ken Baxter and his two pals, Pancho and Panhandle, finding Professor Wahl, injured and wandering on the range. They take him to Blue Mesa Trading Post, where two archaeologists, Dr. Floto and Baron Starkoff, foreign government representatives, are staying. Both want to secure control of a supply of helium gas found in an ancient Indian cave. Wahl, working for the Federal Government, is murder at the Blue Mesa. The land strip on which the cave is located is claimed by Letty and Jim Morgan, brother and sister owners of the Lazy Y Ranch. Tin Cup Ranch owner Joe Larkin hires Ken to take possession of a cabin on the Morgan land in order to gain title. Ken, an undercover G-Man, discovers a secret passageway from the cabin that leads to the cave and discovers the helium, and also that Larkin is working with Starkoff.