The year is 2057. Humanity has raised exploiting the solar system to an art form and Bella Lind and the crew of her nuclear-powered ship, the Rockhopper, are the best at what they do: pushing ice. Near the end of their current mission cycle, startling news arrives from Saturn: Janus, one of Saturn's ice moons, has inexplicably left its natural orbit and is now heading out of the solar system at high speed. Bella Lind and the Rockhopper have been assigned to follow it. But more rurprises are in store, and not all of them are welcome.