SOUNDS. Even if he had made a mistake, and the console's search program failed to locate the recording, it would be somewhere in the machine's permanent, nonerasable memory. There was always the hope
that he might one day find it again by chance, as was happening all the time with information he had filed under MISC.
He decided to let the recording run for another few minutes before completing the interrupted call to
Grandma. As luck would have it, the wind must have slackened at about the time he keyed EXECUTE,
because there was a long, frustrating silence. Then, out of that silence, came something new.
It was faint and distant, yet conveyed the impression of overwhelming power. First there was a thin
scream that mounted second by second in intensity, but somehow never came any closer. The scream
rose swiftly to a demonic shriek, with undertones of thunder — then dwindled away as quickly as it had appeared. From beginning to end it lasted less than half a minute. Then there was only the sighing of the wind, even lonelier than before.
For a long, delicious moment, Duncan savored the unique pleasure of fear without danger; then he
reacted as he always did when he encountered something new or exciting. He tapped out Karl Helmer's
number, and said: "Listen to this."
Three kilometers away, at the northern end of Oasis City, Karl waited until the thin scream died into
silence. As always, his face gave no hint of his thoughts. Presently he said: "Let's hear it again."
Duncan repeated the playback, confident that the mystery would soon be solved. For Karl was
fifteen, and therefore knew everything.
Those dazzling blue eyes, apparently so candid yet already so full of secrets, looked straight at
Duncan. Karl's surprise and sincerity were totally convincing as he exclaimed: "You didn't recognize it?"
Duncan hesitated. He had thought of several obvious possibilities — but if he guessed wrongly, Karl
would make fun of him. Better to be on the safe side...
"No," he answered. "Did you ?"
"Of course," said Karl, in his most superior tone of voice. He paused for effect, then leaned toward the camera so that his face loomed enormous on the screen.
"It's a Hydrosaurus on the rampage."
For a fraction of a second, Duncan took him seriously — which was exactly what Karl had intended.
He quickly recovered, and laughed back at his friend.
"You're crazy. So you don't know what it is?"
For the methane-breathing monster Hydrosaurus rex was their private joke — the product of youthful
imaginations, inflamed by pictures of ancient Earth and the wonders it had brought forth near the dawn of creation. Duncan knew perfectly well that nothing lived now, or had ever lived, on the world that he
called home; only Man had walked upon its frozen surface. Yet if Hydrosaurus could have existed, that
awesome sound might indeed have been its battle cry, as it leaped upon the gentle Carbotherium,
wallowing in some ammonia lake...
"Oh. I know what made that noise," said Karl smugly. "Didn't you guess? That was a ram-tanker making a scoop. If you call Traffic Control, they'll tell you where it was heading."
Karl had had his fun, and the explanation was undoubtedly correct. Duncan had already thought of it,
yet he had hoped for something more romantic. Though it was perhaps too much to expect methane
monsters, and everyday spaceship was a disappointing anticlimax. He felt a sense of letdown, and was
sorry that he had given Karl another chance to deflate his dreams. Karl was rather good at that.
But like all healthy ten-year-olds, Duncan was resilient. The magic had not been destroyed. Though
the first ship had lifted from Earth three centuries before he was born, the wonder of space had not yet been exhausted. There was romance enough in that shriek from the edge of the atmosphere, as the
orbiting tanker collected hydrogen to power the commerce of the Solar System.
In a few hours, that precious cargo would be falling sunward, past Saturn's other moons, past giant
Jupiter, to make its rendezvous with one of the fueling stations that circled the inner planets. It would take months — even years — to get there, but there was no hurry. As long as cheap hydrogen flowed
through the invisible pipeline across the Solar System, the fusion rockets could fly from world to world, as once the ocean liners had plied the seas of Earth.
Duncan understood this better than most boys of his age; the hydrogen economy was also the story of
his family, and would dominate his own future when he was old enough to play a part in the affairs of
Titan. It was now almost a century since Grandfather Malcolm had realized that Titan was the key to all the planets, and had shrewdly used this knowledge for the benefit of mankind — and of himself.
So Duncan continued to listen to the recording after Karl had switched off. Over and over again he
played back that triumphant cry of power, trying to detect the precise moment when it was finally