After that they swam more quietly, keeping together by the faint sounds of each other's breathing and an occasional touch of hands. Every few minutes they stopped and floated motionless, listening and feeling with every fiber of their bodies. Sue felt it first, a tiny, almost unnoticeable pulsation in the black water. She touched Nick's wrist, indicating a direction, and swam a few more strokes. The pulsation grew stronger. Nick felt it too, and only an effort of will kept him from threshing away as tingles of terror oozed along his spine. He felt very naked and helpless and vulnerable as he floated. Again Sue swam a few strokes and stopped. For a full minute she lay quietly, allowing her breathing to ease. Then there was a faint splash as she dived, and it seemed to Nick as though hours passed while he waited alone in the darkness. "Psst!" he hissed softly at the sound of her head breaking surface. She rested a while, dived again, and when she came up this time the pulsations were appreciably stronger. Something below turned and moved uneasily, questioningly, disturbed in its long slumber by their presence. A third time Susan dived. Nick waited, counting seconds. She did not come up. He waited. And still she did not come up. Panic began to grip him. He floundered into a clumsy dive and swam downward through the inky fluid. His ears hummed and his chest began to burn, but his groping hands encountered nothing. At last he fought his way dizzily to the surface. She was just calling him the second time as his head broke water and he gulped a lungful of air. "Nick!" The word was roaring from the rocks as she heard his splash and indrawn breath. "I touched it, Nick! I had to go deep," she panted as she swam toward him. "I think it got my thoughts, just what you told me." Deep in the black lake something huge and unguessably powerful heaved and stirred, creating wavelets that raced toward shore and filled the cavern with insane, reechoing laughter as they broke against the rocks. Racing now, without any attempt at silence, Nick and Susan swam toward the reassuring green pinpoint of light that marked the shelving ledge. The waves were rising, lapping almost to their clothing, as they waded ashore. Without pausing to dry themselves they dressed and dashed up the tunnel. Halfway to the surface they paused to rest, sitting on the cold, curving floor. "What was it like?" Nick asked. In the greenish light he could see her shudder. "I--I really don't know," she confessed. "It was huge and it had no real shape, but some parts were hard and some weren't." "Will it do what we want?" "I--I think so. It was so _different_ that I couldn't understand all its reactions." It was night when they edged out through the narrow opening, but Klev was awake and watching. His jaw dropped in astonishment as Sue told of their journey, of how she had actually touched the water-_vora_. "Martians can't swim, Nick," she explained.