Out of Time’s Abyss begins after Bradley leaves Fort Dinosaur with several companions to explore Caspak, only to be abducted by one of the strange winged Wieroos and carried across the inland sea to their sinister city of Oo-oh. There he meets Co-Tan, a woman of the Galu people from mainland Caspak, and together they attempt to escape while Bradley discovers the Wieroos’ brutal society, their ruler, and the disturbing evidence of the victims on whom their civilization depends. After overpowering their captors and returning toward the mainland, Bradley and Co-Tan struggle to reach Fort Dinosaur, and the story brings the Caspak trilogy to a close by combining lost-world adventure and romance with a fuller revelation of the extraordinary developmental system governing human life in this isolated land.