The SECRET VISITORS — James White

There seemed to be three distinct groups of aliens now. First came the old men, harmless and fanatically uncommunicative, whose behavior had first aroused the department's suspicions. There was the group that had been responsible for the St. Armande fire, a group which almost certainly contained a large number of Earthmen. A third group, possibly of only a few individuals, were opposed to the war-breeding activities of the second group, and they disapproved of their treatment of the old men, who were group one. And, just to tangle the skein further, there was a time-traveling Earthman from two hundred years in the past.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 some connection between himself and 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 that was originating in the farthest stars, or else surrender the Earth unconditionally to THE SECRET VISITORS.