"We're not," I told her. "There's a way out of it, and the simplest way on earth. It's so infernally simple that we've all overlooked it. It narrows down to a simple problem in geometry. Do you remember what the cypher said?"
"'When the Lone Tree, the hut door and the rising sun are in line measure seven feet east. Then face direct north, draw another line at right angles to the previous one, extending for twelve feet. Dig then.'" He rattled through the directions so rapidly that I knew he must have had them off by heart.
"That's it," I said, while the others listened in breathless interest. "Now this is the position to my mind: The line that runs through the doorway, the tree and the sun must go due east. The sun at that time of the year would be due east. Well, all we have to do is to cast our east line, carry it along for seven feet, and then turn so that we are facing direct north."
"And at right angles to the previous line," Moira reminded me.
"It's the same thing," I said. "Direct north runs at right angles to direct east, if you want to know. However, when we've got our north line we follow it for twelve feet, and after that we dig. Quite possibly Bradby made some slight variation—he wouldn't have the necessary instruments to make his figures absolutely exact—but, as I've said before, I don't see that we can go very far wrong. Whatever variation there is won't matter much once we start digging. If we allow a foot or so in all directions we'll be on the safe side. What do you think, Cumshaw?"
"Well," he said slowly, "it sounds feasible enough, and if it turns out as well in practice as it does in theory I'll have nothing to say against it."
"There's only one way of making sure," I said tentatively.
Moira turned on me. "What's that?" she asked with unfeigned interest.
"Trying and seeing for ourselves," I answered. "Here we are, right on the very spot, so why not put it to the test?"
Neither of them answered. A queer, speculative look crept into Moira's eyes and Cumshaw paled a little beneath his tan. It was the crucial moment of the expedition, and the mere adoption of my suggestion meant that in the next few minutes we would be face to face with either failure or success—none of us knew which. While we were in ignorance there was always room for hope, but the instant our investigation was concluded the matter would be settled for good or for evil.