The main character of the novel is Dr. Nile Etland, a young woman of no extraordinary powers (like "psi") but a remarkable combination of intelligence, knowledge, and nerve. A biochemist and native of the planet, Nandy-Cline, on which the novel takes place, Dr.

Etland has arranged to keep tabs on Dr. Ticos Cay, an elderly but very hale researcher into the life-forms of a "floatwood" island, searching for biochemical methods of lengthening the human life-span. It is between her monthly visits to the island a sort of huge jungle adrift on the ocean currents of Nandy-Cline, that the Parahuans, a race of sentient amphibians from an empire adjacent to the Hub, capture Dr. Cay to question him.

Dr. Etland reaches the island with Sweeting, a mutant hunting-otter who speaks, discovers the desperate scam that Dr. Ticos Cay is trying to pull on the Parahuans, and decides that she...