She had never seemed more precious to him and for an instant he could feel his fear lessening a little. But it came back and was worse than before. It was like an old pain returning at an unexpected moment to chill a man with the sickening reminder that all joy must end. His decision to act was made quickly. The first step was the most difficult but with a deliberate effort of will he accomplished it to his satisfaction. His secret thoughts he buried beneath a continuous mental preoccupation with the vain and the trivial. It was important to the success of his plan that his companions should suspect nothing. The second step was less difficult. The mental block remained firm and he succeeded in carrying on actual preparations for his departure in complete secrecy. The third step was the final one and it took him from a large compartment to a small one, from a high-arching surface of metal to a maze of intricate control mechanisms in a space so narrow that he had to crouch to work with accuracy. Swiftly and competently his fingers moved over instruments of science which only a completely sane man would have known how to manipulate. It was an acid test of his sanity and he knew as he worked that his reasoning faculties at least had suffered no impairment. Beneath his hands the Time Observatory's controls were solid shafts of metal. But suddenly as he worked he found himself thinking of them as fluid abstractions, each a milestone in man's long progress from the jungle to the stars. Time and space--mass and velocity. How incredible that it had taken centuries of patient technological research to master in a practical way the tremendous implications of Einstein's original postulate. Warp space with a rapidly moving object, move away from the observer with the speed of light--and the whole of human history assumed the firm contours of a landscape in space. Time and space merged and became one. And a man in an intricately-equipped Time Observatory could revisit the past as easily as he could travel across the great curve of the universe to the farthest planet of the farthest star. The controls were suddenly firm in his hands. He knew precisely what adjustments to make. The iris of the human eye dilates and contracts with every shift of illumination, and the Time Observatory had an iris too. That iris could be opened without endangering his companions in the least--if he took care to widen it just enough to accommodate only one sturdily built man of medium height. Sweat came out in great beads on his forehead as he worked. The light that came through the machine's iris was faint at first, the barest glimmer of white in deep darkness. But as he adjusted controls the light grew brighter and brighter, beating in upon him until he was kneeling in a circle of radiance that dazzled his eyes and set his heart to pounding.