On the planet Winter, there is no gender. The Gethenians can become male or female during each mating cycle, and this something humans find incomprehensible .
The Ekumen of Known Worlds has sent an ethnologist to study the Gethenians on their forbidding, ice- bound world. At first he finds his subjects difficult and offputting, with their elaborate social systems and alien minds. But in the course of a long journey across the ice, he reaches an understanding with one of the Grethenians - it might even be a kind of love...