'It's like a fifth dimension,' Harlan said.
'Whatever,' Pitt said. 'But getting back to what Cassy was telling me, apparently this alien virus is responsible for the mass extinctions the Earth has witnessed. Every time they came back here, the creatures they infested weren't suitable, so they left.'
'And all the creatures they'd infected died?' Sheila asked.
'That's how I understand it,' Pitt said. 'The virus must have made some lethal change in the DNA causing the disappearance of entire species. That created an opportunity for new creatures to evolve. She told me that Beau had specifically mentioned this with regard to the dinosaurs.''
'Well, I'll be,' Harlan said. 'So much for the asteroid or comet theory.'
'How did the creatures die?' Sheila asked. 'I mean, what was the specific cause of death?'
'I don't think she knew that,' Pitt said. 'At least she didn't tell me. But I can ask her later.'
'It might be important,' Sheila said. She stared off into the middle distance with unseeing eyes. Her mind was churning. 'And the virus supposedly came to Earth three billion Earth years ago?'
'That's what she said.'
'What are you thinking?' Harlan asked.
'Is there any anaerobic bacteria available in the lab?' Sheila asked.
'Yeah, sure,' Harlan said.
'Let's get some and infect it with the enabling protein,' Sheila said with mounting excitement.
'Okay,' Harlan said agreeably. He stood up. 'But what's on your mind? Why do you want bacteria that grows without oxygen?''
'Humor me,' Sheila said. 'Just get it while I prepare some more enabling protein.'
Beau threw open the french doors leading from the sitting room to the terrace surrounding the pool. He stepped out and strode across the terrace. Alexander hurried after him.
'Beau, please!' Alexander said. 'Don't go! We need you here.'
'They found her car,' Beau said. 'She's lost in the desert. Only I can find her. By now she should be far on her way to becoming one with us.'
Beau descended the few steps from the terrace to the lawn and struck out toward the waiting helicopter. Alexander stayed at his heels.
'Surely this woman cannot be so important,' Alexander said. 'You can have any woman you want. This is not the time to leave the Gateway. We've not even tested the grids to full power. What if we are not ready?'
Beau spun around. His narrow lips were pulled back in fury. 'This woman is driving me mad. I must find her. I'll be back. Until then, carry on without me.'
'Why not wait until tomorrow?' Alexander persisted.
'By then the Arrival will have occurred. Then you can go look for her. There'll be plenty of time.'
'If she's lost in the desert she will be dead by tomorrow,' Beau said. 'It's decided.'
Beau turned back to the copter and quickly closed the distance. For the last few feet he had to duck under the rotating blade. He climbed into the front seat next to the pilot, nodded a greeting to Vince in the backseat, then motioned for the pilot to lift off.
'How long has it been?' Sheila asked.
'About an hour,' Harlan said.
'That should be enough time,' Sheila said impatiently. 'One of the first things we learned was how fast the enabling protein functioned once it was absorbed into a cell. Now let's give the culture a slight dose of soft X- rays.'
Harlan looked askance at Sheila. 'I'm beginning to get the drift of what's going on in that brain of yours,' he said. 'You're treating this virus like a provirus, which it is. And now you want to change it from its latent form into its lytic form. But why the anaerobic bacteria? Why no oxygen?'
'Let's see what happens before I explain,' Sheila said. 'Just keep your fingers crossed. This could be what we are looking for. An alien Achilles' heel.'
They gave the infected bacterial culture the dose of X-rays without disturbing its atmosphere of carbon dioxide. As they made mounts for the scanning electron microscope, Sheila found her hands trembling with excitement. She hoped with all her heart that they were on the brink of discovery.
With one of his powerful legs, Beau kicked the door of the deserted gas station. The blow tore it from its hinges and sent it crashing into the far wall of the room. Stepping into the dim interior, Beau's eyes glowed intensely. The helicopter ride had done little to temper his fury.
He stood in the semidarkness for several seconds, then turned around and walked back out into the bright sunshine.
'She was never in there,' Beau said.
'I didn't think so,' Vince said. He was bending down in the sand on the opposite side of the aged gas pumps. 'There are some other fresh tire tracks here.' He stood up and looked toward the east. 'There must have been a second vehicle. Maybe they picked her up.'
'What do you suggest?' Beau asked.
'Apparently she hasn't appeared in any town,' Vince said. 'Otherwise we would have heard. That means she's out here in the desert. We know there are isolated groups of 'runners' hiding out in the area who've so far avoided infection. Maybe she joined up with one of them.'
'But she's infected,' Beau said.
'I know,' Vince said. 'That part is a mystery. Anyway, I think we should head east along this road and see if we can find any tracks going off into the desert. There must be some kind of camp.'
'All right,' Beau said. 'Let's do it. Time is running out.'
They climbed back into the helicopter and lifted off. The pilot was ordered to fly high enough to keep from kicking up too much sand and dust yet low enough to see any tracks heading away from the road.
'My gosh, there it is,' Harlan said. They had focused in on a virion at sixty thousand times magnification. It was a large filamentous virus that looked like a filoviridae with tiny, cilialike projections.
'It's awesome to think that we are looking at a highly intelligent alien life form,' Sheila said. 'We've always thought of viruses and bacteria as primitive.'
'I don't think it is the alien per se,' Pitt said. 'Cassy mentioned that the viral form was what enabled the alien to withstand space travel and infest other life forms in the galaxy. Apparently Beau didn't know what the original alien form looked like.'
'Maybe that's what the Gateway is for,' Jonathan said. 'Maybe the virus likes it here so much, the aliens themselves are coming.'
'Could be,' Pitt said.
'All right,' Harlan said to Sheila. 'So this little trick with the anaerobic bacteria worked. We've seen the virus. What was your mysterious point?'
'The point is that this virus came to Earth three billion years ago,' Sheila said. 'At that time the Earth was a very different place. There was very little oxygen in the primitive atmosphere. Since then things have changed. The virus is still fine when it is in the latent form or even when it has been enabled and has transformed the cell. But if it is induced to form virions, it's destroyed by oxygen.'
'Interesting idea,' Harlan said. He looked down at the culture whose top was now off, exposing its surface to room air. 'If that's the case then we'll see damaged, un-infective virus if we make another mount.'
'That's exactly what I'm hoping,' Sheila said.
Without wasting any time, Sheila and Harlan set to work creating a second sample. Pitt helped as best he could. Jonathan went back to playing with the computer-run security system.
When Harlan focused in on the new mount, it was immediately apparent that Sheila was right. The viruses appeared as if they had been partially eaten.
Sheila and Harlan jumped up from their seats and enthusiastically high-fived and then embraced each other. They were ecstatic.
'What a brilliant idea,' Harlan said. 'You're to be congratulated. It's a joy to see science in action.'
'If we were doing real science,' Sheila said, 'we'd go back and exhaustively prove this hypothesis. For now, we'll just take it at face value.'
'Oh, I agree,' Harlan said. 'But it makes such sense. It's amazing how toxic oxygen is and how few laypeople
