OUT FROM THE CLEFT where Mel Gray worked, across the flat plain of rock stripped naked by the wind that raved across it, lay the deep valley that sheltered the heart of the Moulton Project.
Hot springs joined to form a steaming river. Vegetation grew savagely under the huge sun. The air, kept at almost constant temperature by the blanketing effect of the hot springs, was stagnant and heavy.
But up above, high over the copper cables that crossed every valley where men ventured, the eternal wind of Mercury screamed and snarled between the naked cliffs.
Three concrete domes crouched on the valley floor, housing barracks, tool-shops, kitchens, store-houses, and executive quarters, connected by underground passages. Beside the smallest dome, joined to it by a heavily barred tunnel, was an in
