A small distant planet, which, by a strange coincidence, had to become the scene of a bloody war between three races. The people of Earth understand that neutrality cannot be maintained. Superintendent of the environmental police Shan Frankland, who made friends with the powerful alien warrior Aras, decides to join her people on the side of his people, trying to stop the invasion of the planet by conquerors. As a reward, Aras endows her with a mysterious symbiont, providing its bearer with almost complete invulnerability. But this generous gift brings Shan only new trials - because from now on she is hunted by those who want to take advantage of her abilities , and those who want to destroy her as a dangerous mutant...