As this spectacular, large-scale space opera opens, Janus, a moon of Saturn, now revealed as an alien artifact, has suddenly left orbit and headed for interstellar space.

The Rockhopper, a comet miner commanded by Capt. Bella Lind, is the only spacecraft in the solar system positioned to catch the huge alien machine. Though a short exploration is all that's planned, the Rockhopper soon finds itself trapped in Janus's time- and distance-distorting slipstream. Determining that Janus is heading toward an even more gigantic artifact orbiting the star Spica, the comet miners settle down to form their own castaway civilization, a process marred by the bad blood between those who support Captain Lind and those who blame her for their fate. Janus soon proves itself to be an incredibly strange and ever changing environment. Eventually, the castaways reach the Spica artifact, encounter several very alien species and discover that their fate is even stranger than they could have imagined.