2057. Humanity has raised exploiting the solar program to an art form. Bella Lind as well as the staff of her nuclear-powered ship, the Rockhopper, drive glaciers. They mine comets. And they’re proficient at it.

The Rockhopper is nearing the end of its current objective cycle, and everyone is in need of some much-needed R & R, when startling news arrives from Saturn: Janus, one of Saturn’s ice moons, has inexplicably left its natural orbit and is currently heading out of the solar system at high speed.

As layers of camouflage fall apart, it becomes very clear that Janus was by no means a moon to begin with. It’s some kind of machine-and it is today headed toward a fuzzily glimpsed artifact 260 light-years away. The Rockhopper may be the only dispatch anywhere near Janus, and Bella Lind is certainly ordered to shadow it for the few essential days before it falls forever out of reach.

In accepting this mission, she sets her dispatch and her crew on the collision course with destiny-for Janus has more surprises in store, and not all of them are welcome.