Schofield watched the three Marines as they reached for their face masks and prepared to jump into the murky pool。 Then he turned and scanned the pool； empty save for the diving bell that hovered out in the center。 The pod of killer whales had left the area about forty minutes ago and hadn't been seen since。 As he gazed at the pool； however； he felt someone tap him on the shoulder。 Schofield turned。
And saw Sarah Hensleigh standing in front of him。 Dressed in a figure…hugging blue…and…black thermal…electric wet suit。 Schofield was momentarily taken aback。 For the first time that day； he noticed just how shapely Sarah Hensleigh was…the woman had a great body。
Schoheld raised his eyebrows。
〃This is what I wanted to ask you about before；〃 Sarah said。 〃When we were outside。 But I never got a chance。 I want to go down with them。〃
〃I can see that；〃 Schofield said。
〃This station lost nine people down in that cave。 I'd likd to know why。〃
Schofield looked from Hensleigh to the three Marine divers on his left。 He frowned； doubtful。
〃I can help；〃 Sarah said quickly。 〃With the cave； for example。〃
〃How？〃
〃Ben Austin…one of the divers who went down there at the very start…said it was an underground cavern of some sort； right？〃 Sarah said。 〃He said it had sheer ice walls and that it stretched off for several hundred feet。〃 Sarah stared at Schofield。 〃My guess is that if the walls in that cave are sheer； then it's a good bet that the cave was formed by some kind of seismic event in the past； some kind of earthquake or undersea volcanic eruption。 Sheer walls are created by sudden upthrusts of rock； not slow； gradual movement。〃
〃I'm sure my men will be safe from sudden upthrusts of rock； Dr。 Hensleigh。〃
〃All right then。 I can tell you what's down there；〃 Sarah said。
That got Schofield's attention。 He turned to the three divers standing by the edge of the pool。 〃Montana； Gant； Cruz。 Just hold on a minute； will you？〃 Schofield turned back to face Sarah Hensleigh； his eyes serious。 〃All right； Dr。 Hensleigh； tell me what's down there？〃
〃All right；〃 Sarah said as she collected her thoughts。 She'd obviously thought about this a lot； but now Schofield had put her on the spot。
〃Theory One；〃 she said。 〃It's alien。 It's a spacecraft from another planet； from another civilization。 Now； that's not really my field…it's not really anyone's field。 But if that thing is alien then I'd give my right arm to see it。〃
〃Mother already gave her left leg。 What else？〃
〃Theory Two；〃 Sarah said； 〃it's not alien。〃
〃It's not alien？〃 Schofield raised an eyebrow。 That's right；〃 Sarah said。 〃It's not alien。 Now this theory； this theory really is my field。 This is pure paleontology。 It's not a new theory by any means； but until now； no one's been able to find any evidence to prove it。〃
〃Prove what？〃
Sarah took a deep breath。 〃The theory goes that once； a long time ago； there was civilized life on Earth。〃
She paused； not for effect； but rather to wait for Schofield's reaction。
At first； Schofield didn't say anything； he just thought about it for a moment。 Then he looked at her hard。 〃Go on。〃
〃I'm talking about a long time ago；〃 Sarah said； gaining momentum。 〃I'm talking before the dinosaurs。 I'm talking four hundred million years ago。 Now； when you think about it。。。 when you think about it in terms of human evolution； it's really very possible。
〃Human life as we know it has been on Earth for less than a million years； right？ Historically speaking； that's not a long time。 If the history of the Earth were the twenty…four hours in a day； then the period of modern human presence would amount to about three seconds。 What we would call civilized human life…human life in its Homo sapiens form…has been here for an even shorter period of time； not even twenty thousand years。 That's less than a second on the world's time clock。〃
Schofield watched Sarah Hensleigh closely as she spoke。 She was excited； speaking quickly。 She was in her element。
〃What paleontologists usually say；〃 she said； 〃is that a whole matrix of factors contributed to the rise of the mammals； and hence the rise of human life on Earth。 The right distance from the sun； the right temperature； the right atmosphere； the right oxygen levels in the atmosphere； and； of course； the extinction of the dinosaurs。 We all know about the Alvarez theory； how an asteroid slammed into the Earth and killed all the dinosaurs and how the mammals rose out of the darkness and took their place as the rulers of the world。 What if I was to tell you that there is evidence that there were at least four other such asteroid impacts on this planet in the last seven hundred million years。〃
〃Asteroid impacts；〃 Schofield said。
〃Yes。 Sir Edmund Halley once suggested that the entire Caspian Sea was created by an asteroid collision hundreds of millions of years ago。 Alexander Bickerton； the famous New Zealand physicist who taught Rutherford； hypothesized that the seabed of the entire South Atlantic Ocean…between South Africa and South America…was one great big bowl…shaped crater； caused by a massive asteroid impact over three hundred million years ago。
〃Now； if we assume…as we so readily do in the case of the dinosaurs…that every time one of these cataclysmic asteroids hit the Earth a civilization died； we can only ask； what other kinds of civilizations； like that of the dinosaurs； have also been destroyed？ What several academics have suggested in recent years…Joseph Sorenson from Stanford is the most well known…is that one of these civilizations may have been human。〃
Schofield looked at the other Marines on the deck around him。 They were all listening to Sarah intensely； rapt in her story。
Sarah went on。 〃You see； on average； the Earth tilts on its vertical axis half a degree every twenty…two thousand years。 What Sorenson postulated was that about four hundred million years ago the Earth was tilted at an angle not unlike the angle it's tilted on today。 It was also no farther from the sun than it is now； so it had similar mean temperatures。 Ice core samples； like the ones we get from this station； have shown that the air was a mix of oxygen； nitrogen； and hydrogen； in quantities very similar to that of our own atmosphere today。 Don't you see it？ The matrix was the same then as it is now。〃
Schofield was slowly beginning to believe what Sarah was saying。
Sarah said； 〃That cavern down there is fifteen hundred feet below sea level； that's two…and…a…half thousand feet below the average land level of Antarctica。 The ice down there is easily four hundred million years old。 If it's upthrusted ice from deeper down…ice that was raised by an earthquake or something…then it could be a lot； lot older。
〃I think that whatever is down there is something that was frozen a long time ago。 A long time ago。 It could be alien； it could be human； from human life that existed on this planet millions of years ago。 Either way； Lieutenant； it'll be the greatest paleontological discovery this world has ever known and I want to see it。〃
Sarah stopped； took a deep breath。
Schofield just stood there； silent。
Sarah spoke softly。 〃Lieutenant； this is my life。 This is my whole life。 Whatever's down there is perhaps the greatest discovery in the history of mankind。 I've been studying my whole life for this…〃
Schofield looked curiously at her； and she cut herself off； sensing that he was about to speak。
〃What about your daughter？〃 he said。
Sarah cocked her head。 She hadn't expected him to ask that。
Schofield said； 〃You're willing to leave her up here alone？〃
〃She'll be safe；〃 Sarah said evenly。 Then she smiled。 〃She'll be up here with you。〃
Schofield hadn't seen Sarah Hensleigh smile before。 It illuminated her face； lit up the whole room。
Sarah said； 〃I'll also be able to identify our divers who went down to that cave before； which might be…〃
Schofield held up his hand。 〃It's all right； you convinced me。 You can go。 But you use our scuba gear。 I don't know what happened to your people down there before； but I have a sneaking suspicion that whatever's down there heard the noise of their breathing gear and I don't want the sa