Will our first contact with aliens be the dawn of a new tomorrow -- or the last act in human history? The moon has suddenly acquired its own satellite: a two-mile-across starship that represents a hitherto unsuspected Galactic Commonwealth. The F'thk, a vaguely centaur-like member species for whom Earth's ecology is hospitable, have been sent to evaluate humanity for prospective membership. The F'thk are overtly friendly but very private - "Information is a trade good." As Earth's scientists struggle to understand their secretive appraisers, odd inconsistencies emerge. As troubling as those anomalies is the re-emergence of a bit of insanity humanity thought it had outgrown: Cold War and nuclear saber-rattling. The Galactics' arrival may signify the start of a glorious new era, or it may presage the cataclysmic end of human civilization. Which outcome do the aliens really desire ... And what will they do if humanity refuses to play its assigned role?