Elderly people die in hospitals and their bodies disappear, only their loved ones notice and worry about it. However, some are seen months later, alive and rejuvenated, but they seem alien and indifferent to the world around them, they don't recognize anyone, they are living a new life. A former police officer, Sol Grass, sets out to solve this mystery. What he discovers turns his life upside down. He encounters the Sihils, who need bodies adapted to the planet's biological richness in order to live on Earth. Earth is teeming with biological diversity; life is everywhere, abundant and easily wasted. Some of the Sihils join forces with humans to resist this insidious invasion. They aspire to blend in with humanity. Can this curious alliance save humanity?