Myles Standish Cabot, radio genius, who solved the secret of the wireless transmission of matter, returns to Earth from the planet Venus, who inhabitants, the Cupians, are much like men, except that they have antennae instead of ears, and communicate by radio. Cabot relates how the conquered Formians, giant, intelligent ant-men, conspired with Prince Yuri, a renegade Cupian, and his followers to again take control of the planet.