Frank Glenn was one of the two astronauts sent to Planet X by the World Space Administration, in the year 196X. There he and Ken Fuji were met by the Controller of Planet X who told them of X's problem with King Ghidorah, and upon returning to Earth Glenn and Fuji relayed the Controller's desire to borrow Godzilla and Rodan. During this time, Glenn met and fell in love with a mysterious woman named Namikawa.
She however as it turned out was an Xian spy who reported to the Controller's second-in-command. Before she was killed by her superiors for violating Planet X's laws forbidding emotion, and he captured, Namikawa gave Glenn one of Tetsuo Teri's sonic devices. Using this, Glenn escaped from the Xians' custody along with Tetsuo and was able to inform Fuji and Dr. Sakurai of the aliens' weakness to high-pitched sounds.