Military documentary of how during WWII overseas mail was delivered.

While Clutch is at an in-store signing for his new book he gets a telegraph telling him he must go to South America to find a lost friend.

Two escaped convicts are found hiding in a rocket ship built by a renegade inventor, who forces them to become the crew for a trip to the Moon. Also on board, as inadvertent stowaways, are his assistant and his secretary; and none of them are aware that the inventor is actually a Lunarian explorer sent to Earth by the dying Lunar civilization.