[A story of the "Hainish" series, set in the same Universe as "The Left Hand of Darkness".] An experimental faster-than-light ship is about to embark on its first test run with a real crew on board. Successful tests have been conducted with robots and non-intelligent animals, but the alien physicists who designed the ship guardedly caution the mixed crew of human and aliens of the temporal risks ... because they are unable to explain how the ship's transilient virtual field actually works. Locus Poll Award Nominee, Nebula Award Nominee