'The Mohole Mystery' (1968) [also published as 'The Mohole Menace'], by Hugh Walters, a British science fiction author, is the 11th Volume (of 20) in the "Chris Godfrey of UNEXA" series (UNEXA is the fictional United Nations Exploration Agency). These are strong stories of interplanetary adventure, well written, aimed at anyone with an interest in the actual Space Race of the 1960s. Of his writing, Walters said: "A good SF story should (1) entertain, (2) educate painlessly, and (3) inspire young people of today to be the scientists of tomorrow". His early novels in this series deal with the exploration of other planets in our solar system; written for a youthful audience, they are nonetheless strongly grounded in the real science and politics of the time. Later volumes in this series are more speculative novels, concerning alien visits, once all the solar planets have been explored. Although some of the science and spaceflight technology featured is fictional, he never departs from science for the realms of fantasy. The main characters in this International series are two British astronauts, one American astronaut, and one Russian cosmonaut; respectively Chris Godfrey, Tony Hale, Morrey Kant, and Serge Smyslov. Initially, the focus is on Chris Godfrey, hence the overall series is named after him. He is the continuing thread which binds the series together, being the only character to appear in every volume. Although this is a .PDF format file, it is in fact a text file, not a set of page images.