Nathan Gregory is a World War I veteran pilot who runs a small, debt-ridden traveling carnival along with loyal daughter Jean. Gregory is at odds with five of his former squadron comrades, who he thinks shot him down in 1918 and stole his plans for an incredible invention, a radio=piloted plane. An enigmatic criminal, called "The Eagle", and his gang of toughs skywrites threatening the five businessmen with vengeance for their past misdeeds. Although Gregory is suspected of being the arch-villain, especially after he disappears, hero Craig McCoy and the carnival's midget, strongman, and ventriloquist struggle to expose "The Eagle's" identity.