The Wardens of Earth sometimes unbar strange windows, I suspect - windows which face on other worlds than ours: and They permit this-or-that man to peer out fleetingly, perhaps, just for the joke's sake; since always They humorously contrive matters so this man shall never be able to convince his fellows of what he has seen or of the fact that he was granted any peep at all. The Wardens without fail arrange what we call - gravely, too - 'some natural explanation.'