This, the seventh and final book in the "Tom Corbett" series by "Carey Rockwell" (whoever he was in real life) -- is, like all of the "Tom Corbett" books, something special. It's another tale of the three young men who serve in the Solar Guard as Space Cadets. It starts with cadet Roger, urm, nicking a study spool for use in a competitive exam -- but that leads all of our cadets into a fight, and when they're caught at that, a trial. In the midst of the trial they get assigned to duty on a Top Secret Projectile Project, and things go wrong there in ways at once related and impossible to connect. Someone is causing real menace to roost in the cadets' lives, and the worst is still ahead . . .