Henshaw gestured with his own sandwich. 'Go on. Let's have 'em.'
Indy glanced at Gale. 'Anytime you feel I'm missing something, step in,' he instructed her.
She nodded. She would wait until she had something worth saying or asking.
In the meantime, she knew she was in for an education. She knew how to fly an airplane, even one so large as the threeengined Ford. But she knew she was about to step into an area where she was a neophyte. Whatever Indy might advance would be measured and evaluated, and the response given, by Harry Henshaw—who was as much a technical intelligence specialist as he was a highly experienced pilot in everything from small trainers and fighters to huge transports and bombers.
'Let's start with the zep,' Indy said. 'Harry, I want you to consider any statement I make as much of a question as it is a conclusion. You teach me about wings and things and I'll take you smoothly through tombs and pyramids.'
Henshaw laughed. 'It's a deal.'
'Okay,' Indy said, 'the zep. Treadwell explained that they got at least three fighters into position to empty their guns into that thing.'
'Right,' Henshaw said.
'And they fired tracers,' Indy went on quickly. 'Which means, one, they didn't hit the liftinggas cells.'
'Possibility, yes,' Henshaw replied. 'Well, if that thing is lifted by hydrogen, then either it's got heavy shielding about the gas bags, which kept the tracers from hitting them—'
'Dismiss that,' Henshaw waved away the suggestion. 'You're talking so much weight the thing could hardly get above the treetops.'
'Got it,' Indy said, nodding. 'Or the fighters could have missed completely.'
'Nope,' Henshaw countered. 'I checked. The pilots saw their tracers going into the top of the hull.'
'Then either those people aboard the airship were incredibly lucky,' Indy said, hesitating before finishing his sandwich, 'or they weren't using hydrogen, or any other flammable gas.'
'Congratulations,' Henshaw told him.
'That means they're using helium,' Indy came back. 'So where are they getting it?'
'I thought you Yanks had a world monopoly on helium,' Gale offered.
'We sure do,' Henshaw told her. 'The main source is—'
Indy gestured to interrupt. 'Let me,' he told Henshaw. 'I've been doing some homework on this.'
Henshaw seemed amused with Indy's intensity. 'Have at it, Professor.' He smiled.
'Mineral Wells, Texas.'
'Congratulations,' Henshaw said, clearly impressed. 'But there are also helium storage points—'
'Too crowded,' Indy said quickly. 'Too obvious. They can't move something the size of a small mountain where people would go bananas at the sight of a huge gleaming airship zipping along without engines.'
'So they must have a base that completely conceals that airship?' Gale asked.
'Give the lady a cigar,' Indy said. 'You know,' he turned back to Henshaw,
'each clue opens the door a bit wider to more answers.'
'Always does,' Henshaw agreed. 'A matter of the picture becoming clearer as you fit each piece into the jigsaw puzzle.' He eyed Indy with a quizzical look. 'Do I get the idea we've heard only part of your conclusions?'
Indy smiled. 'I know this may sound crazy, but it looks as if a mixture of anthropology and archeology has the answer we're after. That, and some old but very powerful superstitions, the latter enough to convince eyewitnesses to the airship to keep it a secret.'
'You're way ahead of me,' Henshaw said, irritated that he wasn't following Indy fast enough.
'Well, one of the best kicks to open the door came from Filipo Castilano,'
Indy said. 'Remember when Treadwell told us that Filipo had made vague references to a city in the sky? At best it seemed terribly tenuous. For all I knew, Filipo was deliberately disguising his message. Likely he figured I would extrapolate from what he was hinting at and come up with the answer he wanted me to get.'
'And did you?' Henshaw pressed.
'Not at first,' Indy admitted. 'A city in the sky could be Asgard. Home of the gods. It might be Mount Olympus.
Every culture has some land of city, or Eden, or heaven in the sky. But I had to keep in mind that Filipo could have been speaking more literally than I suspected.'
'Indy, you're playing games with us,' Gale complained.
'No; not really. I'm trying to have you accompany me on the process I was using to come up with the right answer.'
He ticked off the items on his fingers. 'First, the airship can't possibly be using hydrogen. It would have been blown apart by now with its own jet engines. Plus the fact
that it has—it must have—a huge open ramp at its stern, so that the discs can come in to be recovered. And they're also pouring out very high heat.'
'Agreed,' Henshaw said. 'Even a minor hydrogen leak would be a disaster.'
'Okay,' Indy went on. 'So we need helium. Shipping great quantities of helium out of the U.S. would attract too much attention. The government is paranoid on the stuff. But there's no problem in shipping helium by the
