After thousands of years away from Earth, an advanced group of men have returned, forever changed for the better. In this continuation of the Martian Symbiont series, the men rediscover family and find friendship. Each man has evolved to include a symbiont-a telepathic entity swimming through his circulatory system, keeping him peaceful, healthy, and empathetic. Now, twenty years later, 92 percent of Earth's population has a symbiont, as men married and had children with human women. But will peace remain?
An inscrutable, yet hostile alien species is about to invade Earth's tranquility, shattering that peace. The small minority of nonsymbiont humans are skeptical, believing the invasion is a way to frighten people into submission. When they further learn that a nonhuman, non-Martian alien has been living among them disguised as a human for twenty years, the tension thickens.
This one unique being, Lyle, has the knowledge and benevolence to save the planet from ruin. Assuming his natural form, he joins the effort to stop the aliens. Although he has struggled to find his place in the human/Martian world, he will soon discover what his purpose is and how he must achieve it.