With a lasting peace established between Earth and Baltan mediated by the growing alliance with the mysterious Szzzyyyxx, a new chapter in human history begins. But in the midst of this, the Szzzyyyxx Mother requests Sally's help with a mystery. Two Szzzyyyxx vessels have disappeared in the far reaches of their space. Sally and Ian plan a controversial rescue mission with the first of a new line of experimental ships. They arrive in the region to discover a fold that doesn't appear to go anywhere. On closer inspection, however, they find evidence of a black hole and a strange world...