It was just before Summertide, the time when the twin planets, Opal and Quake, would orbit closest to their sun, subjecting both—Quake in particular—to vast tidal forces. It was to be the most violent Summertide ever, creating something that only happened every 350,000 years.

Access to the unstable Quake was supposed to be prohibited, but some very insistent travelers were determined to make the trip. Professor Darya Lang, who studied artifacts left by the long-vanished aliens called the Builders, had a hunch that she might find the Builders themselves. Louis Nenda and the Cecropian Atvar H'sial had their own interests in Quake, and would do anything to get there. And Councilor Julius Graves was hunting murderers—if they were hiding on Quake, he would find them.

Planetary Administrators Hans Rebka and Max Perry had no choice but to go to Quake—risking their lives to protect the others—and to learn, just maybe, the secret of Summertide and the Builders ...