“We start the search now, Olaf,” I said. “And first, O’Keefe, let us see whether the grey stone is really here. After that we will set up camp, and while I unpack, you and Olaf search the island. It won’t take long.”

Larry gave a look at his service automatic and grinned. “Lead on, Macduff,” he said. We made our way up the steps, through the outer enclosures and into the central square, I confess to a fire of scientific curiosity and eagerness tinged with a dread that O’Keefe’s analysis might be true. Would we find the moving slab and, if so, would it be as Throckmartin had described? If so, then even Larry would have to admit that here was something that theories of gases and luminous emanations would not explain; and the first test of the whole amazing story would be passed. But if not⁠—And there before us, the faintest tinge of grey setting it apart from its neighbouring blocks of basalt, was the moon door!