 After witnessing the total destruction of a town called Tonka Flats, agents West and Gordon receive a further threat to destroy the city of Denver. Demanding a ransom, Dr. Horace Humphries, alias "The Falcon", plans to fire a single shell from a falcon-shaped canon toward this western city. West and Gordon go to an underground hide out in search of the destructive canon. But once inside, the agents discover syndicate leaders from foreign countries bidding to purchase the massive weapon for their own use.