by Tom English (Introduction by), Louis Glanzman (Illustrator), Willy Ley (Author)

Tom Corbett, Roger Manning, and the big Venusian Astro have triumphed over the perils of interplanetary pirates, rogue reactors, and hostile environments. But when the Polaris is assigned to lead a "wagon train" of ships to colonize a distant world, the cadets find themselves in a dangerous situation that could finally signal the end of the "best unit" in the Academy. After Captain Strong abruptly departs under strange circumstances, Tom and his pals get entangled in a secret plot involving a belligerent scientist, a suspicious politician, and a planetary anomaly that crashes spaceships. And now the clock is ticking: the cadets can either solve this mystery fast ... or face some truly unpleasant consequences. (Book 4 in the Tom Corbet, Space Cadet series)