1968. It is decades since Mars waged war on Earth, and the major nations have access to Martian-derived technology, but Britain is still recovering from Martian bombardment in the 1940s, when much of the south of England was destroyed. This was followed by the arrival in the 1950s of two million Venusians, seeking refuge from Martian occupation. Now, the Martians are on the attack, and Earth is seeking allies in Jupiter..