When the World Security Organization asked Doctor Lockhart to treat their mysterious prisoner, they hadn't known that the dying old man would reply to their questions in a totally unknown language. They had expected the stranger to reveal something about the world war which seemed imminent. But they had been thinking in terms of foreign spies - not alien beings! Now suddenly they found themselves confronted with a Gargantuan task. They had to find a way to another world, a means of communicating with creatures they could barely imagine. They had to stop a war which was originating in the farthest stars - or else surrender the Earth unconditionally to THE SECRET VISITORS.