Taking off at the last minute, the Jupiter 2 and its crew (including Debbie the Bloop) barely avoid being destroyed along with their foster planet by a massive comet. Damaged by the near collision and in search of replacement parts for the space-drive, the ship docks with a massive alien spaceship that turns out to be an automated prison full of frozen felons. The central premise is promising, especially when it's discovered that the prison's clock as long ceased to function and the convicts are overdue for release, but little clever is done with the intriguing premise. As the season 3 opener, the episode is a welcome return to 'space-opera' (as opposed to the planet-bound monster-of-the-week stories that characterised season 2) but there is still little science in the fiction (the threatening comet and passing super-nova make no astronomical sense and the idea that the felons would be frozen in possession of their weapons is ridiculous). On the plus side, John and Don are given more to do, Robbie the Robot guest stars as an automated prison-guard, and Marcel Hillaire is entertainingly menacing as Phanzig, a strangler foolishly thawed out by (who else?) Dr. Smith. All in all, an OK start to the final season but the show's budgetary limitations are still apparent and too much running time continues to be spent on Dr. Smith's silly antics.