After leaving Earth, now devastated by an alien attack, and exploring the galaxy, Clover Martinez and her fellow teen survivors return home to find crystal formations in the soil that are threatening to destroy the planet, and a colony of survivors who are not who they seem. Clover Martinez and the Last Teenagers on Earth are exploring the galaxy after leaving Earth behind, even if they are homesick. When their ship receives a distress signal from their former home, they arrive to find strange crystal formations are taking over Earth's soil and threatening to destroy the planet. They discover a colony of survivors in the mountains, but relief gives way to panic as the teenagers realize these survivors aren't who they seem-- and there may be no escape. -- adapted from jacket

Series information from goodreads.com Sequel to: The last 8.