Two escaped convicts are found hiding in a rocketship 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 and the only remaining male member of that civilization.

Ex-con turned private investigator Bradford Galt suspects someone is following him and maybe even trying to kill him. With the assistance of his spunky secretary, Kathleen Stewart, he dives deep into a mystery in search of answers.