It's the year 2068. Danny, Emily and Carl, and their parents Mary and Ken Newman are living on Mars when they learn that over 20 Kuiper belt planetesimals from beyond the orbit of Neptune are hurtling toward Earth and Mars. The people of Earth, Mars and its moons work to send asteroids beyond the orbit of Mars to deflect the incoming planetesimals. There may be too many to deflect. Even worse, this plan becomes thwarted when a dissident faction on Mars sabotages the asteroid launch plans, leaving the future of humanity uncertain.