Tenebra is a planet near the triple point of water; small changes of temperature and pressure cause major phase changes. By accident, two children – one human, one non-human – are marooned, creating an interstellar political crisis. Their only hope lies with the Tenebrans themselves, but some may be hostile.
Hal Clement (1922–2003) was the pseudonym of the exemplar of hard science fiction, Harry C. Stubbs. He created the pseudonym while working for his Master's degree in Astronomy at Harvard, fearing his professor would not want him to be "wasting" his time. He did not know that this same professor submitted science fiction to Hugo Gernsback's magazines. Hal's first published story was "Proof" which appeared in the June 1942 issue of Astounding Science Fiction. Then, like many other sf writers, the War intervened.
Following bomber combat duty in Europe with the Army Air Corps in World War II, Harry returned home, learned to drive a car, became a high-school chemistry teacher, and wrote Hugo-winning science fiction.
Hal was a fixture at many SF conventions, where he always had time to talk to his fellow fans.