Earthman Carson Napier had found his share of adventure on the cloud-shrouded planet of Venus. He had rescued his beloved Princess Duare from one peril after another. But when Carson finally restored Duare to her home in the lofty kingdom of Vepaja, she was sentenced to death for daring to love a lesser mortal! Once again, Carson rescued the Princess, snatching her from her own father's palace in an airship of his own devising.

The two outlaws searched the misty skies of Aptor for a refuge, but found only trouble. From the country of the amphibian people to Voo-ad, the city of human amoebae, they faced dangers beyond imagining.