While trailing Forest Ranger Carter (Jason Robards)¸ who is suspected of permitting lumber man Henry Mitchell (Douglass Dumbrille)to cut restricted timber¸ Gene (Gene Autry) fires at a dangerous mountain lion and apparently kills Carter. Actually¸ Bill Wright (Damian O’Flynn)¸ Mitchell’s associate¸ killed Carter because the ranger had discovered tussock moth infestation in the forest¸ and if the infestation was not reported¸ the trees would die and have to be cut¸ thereby profiting Mitchell and Wright. In order to compensate the best he can¸ Gene sells his sportsman’s camp and gives the money to Carter’s daughter Helen (Patricia White.) En route to Texas¸ Gene discovers the infestation and is assigned by the Forest Department to supervise the program of spraying the area with DDT from the air. After the first day of spraying¸ the DDT is blamed by furious stockmen for the many animals found dead of poisoning. Gene suspects a strange plane heard flying in the night was responsible. Gene’s friend Joe Lucas (Jimmy Lloyd)¸ after quarreling with Gene¸ is suspected of flying the phantom plane to discredit Gene’s spraying program. The innocent Joe discovers the plane hidden at Mitchell’s Mill and is shot by Wright. Gene heads for a mountain cabin to confront Mitchell who is waiting to kill him. Joe flies to warn Gene of the trap but Wright is also in the plane.