"John Wilson."

Ray looked around, counting the people. He didn't look too closely at the game, and John suspected he didn't care.

"How long is a game?"

"Three minutes, seven max."

"How much per game?"

"Fifty cents. They play to ten."

"What kind of deal you want?"

"We split the money fifty-fifty."

Ray nodded. "You'll need a license from the city."

"I've already got the paperwork."

"Deal."

They shook.

CHAPTER 24

John found himself thinking more and more about the antimatter source in the device. Somewhere within the device was a pinpoint of gamma radiation, perhaps used to power it. He didn't have the equipment to take an X-ray of it, and at first he had worried that an X-ray might harm the device. But he knew that a tomogram of the interior of an object could be taken by using a point source pa.s.sed through the device at various angles. The images of the sections were put back together to make the tomogram. Why couldn't he use the source within the device as the source for the tomogram? Because he had not the first clue how to do it. He did know one grad student who might know.

When John asked Alex Cheminov about his idea to use tomography for a special project, Alex listened emotionlessly, his hands in the pockets of his tattered jeans, then said, "You'll need collimated beam."

"Why?"

"You've got a point source, right?" He held up a pencil. "Eraser is source. Radiation comes out of source in all directions isotropicly, decreases with one over r-squared. Further you get from source, more scatter your detector picks up from gammas that don't come directly from source. Collimator blocks those scattered gammas, reduces noise. You'll get a better image. Clearer. I worked on same in Russia."

"How long will my collimator need to be?"

"Fifteen centimeters, maybe twenty."

"What should I make it out of?"

He pointed to the storeroom. "Some in there. Take one. Fits right over the detector."

"Thanks, Alex."

He shrugged, his face slack. "No problem."

John borrowed the whole setup, collimator and detector. From what he'd read, he'd need to take long measurements because his source was so small. And he'd have to take many measurements. He decided that he'd need a measurement every fifteen degrees around the diameter of the device. That was twenty-four measurements. He decided to do one per night.

Where he would do it was a problem. He couldn't do it at his apartment. Casey was staying over every few nights. And after he'd reacted the first time she'd seen his notebook, he couldn't afford to let her see any more. The lab bench that the team was using for the pinball machine, however, had a deep drawer. He could set the device in there for twelve hours each night and get a decent reading, he hoped.

Then he would reconstruct the inside of the device. Anything that looked interesting he could reconstruct with finer detail or at oblique angles. It would take a while, but he would have an image of the inside of the device, without ever opening it up.

The calculations were not particularly hard, but there were a lot of them. And there was more than one type of tomography reconstruction algorithm. He found himself begging off two dates in a row with Casey to struggle through a textbook on the subject, but by the third day he seemed to have worked out the equations he'd need to build the reconstruction.

He started taking measurements, showing up late to set up the counter. He had to make clear notes on what angles he took the measurements on and be precise on what the counts were at the exact twelve hours in length.

After he had six measurements, John sat down with a calculator and started figuring. He wished he had a computer, but the computers in this universe were like those from the sixties in his universe, big hulking things used for inscrutable government activities. He had to do the calculations by hand.

The result of three hours of number crunching was a grid of blobs. He realized quickly that having too few measurements produced false images. He saw six regularly s.p.a.ced blobs inside the device, and he couldn't determine which were false and which were true. He filed his drawing away.

Two weeks later, he tried it again, only this time it took him two days of work to back out the results. But it was much more successful. The inside structure was clearer. There were two main round areas of attenuation inside the device, one near the center, under the middle b.u.t.ton, and one halfway between the center and the lever. There were also a number of smaller lumps.

Studying the drawing, he noted that the device was mostly empty s.p.a.ce, or very weakly attenuating material.

He decided to do the same set of measurements at a slightly higher plane. John had a cross section of the things at the mid-plane, but he didn't know if the shapes were cylindrical or spherical.

He returned to the device one morning to find his drawer empty.

A wave of panic pa.s.sed through him.

The device was gone!

f.u.c.k! I should have locked it!

John spun around. The lab was empty, except for someone making a racket with the lathe in the bay one over.

John ran over there. A grad student was at work on a piece of wood, carving into it a series of grooves. She looked up when he waved his arms.

"I'm sorry for disturbing you," John said. "Did you see anyone in that lab bay over there?"

"No, sorry," she said, bending back over her work. Then she stood back up. "Well, Professor Wilson was there, which was odd since it's so early in the morning."

"Wilson!"

John turned and ran out of the lab. He ran down the connecting hall to McCormick Hall, then up the stairs two at a time. Wilson's light was on, his door closed.

John paused to knock, then instead pushed the door open.

Professor Wilson looked up. On his desk was the device. He had a screwdriver out and was attempting to lever the device open.

"What are you doing?" John cried.

"Is there a radioactive source in here?"

" 'What are you doing?' I said," John repeated. He stepped forward and reached for the device.

Wilson pulled it back. John had a moment's flashback to the arguments he'd had with other versions of Wilson. John didn't want to play games.

"You can't have a radioactive device in the lab without permission," Wilson said. "And don't try to attack me. It'll be the end of your academic career."

"Watches use radium. Bananas have pota.s.sium," John said. "Those are no more radioactive than this. You're just trying to hide the fact that you stole my equipment. Hand it over."

"It's my lab; it's my equipment," Wilson said.

"You know that's a lie," John said.

"Don't speak to me that way!"

John stared at Wilson and reached across the desk. Wilson jumped back, but John grabbed the phone. He spun it around.

"I'm calling the police," John said.

"Do it. Campus security will see things my way."

"The real police," John said. He hit 9 to get an outside line. The phone emitted a steady tone.

Wilson just stared at him.

John dialed 911.

"This is the operator. What is the nature of your emergency?"

John paused.

Wilson stared at him.

"Mr. Wilson? Is there an emergency?"

Again neither moved.

"I'll send a patrol car to investigate."

John opened his mouth to urge them to hurry, but Wilson spoke up. "I'm sorry. This is Professor Wilson. I seem to have hit the wrong b.u.t.ton by accident."

"Thank you, sir. Have a good day."

The line went dead.

John held out his hand.

Wilson smiled meekly, then placed the device onto John's palm. He shoved the device into his backpack and turned to go.

"What is it, John?" Wilson asked. "Tell me."

"I told you once, and you didn't believe me."

He'd left the collimator and the detector in Wilson's office. He didn't bother to get a new one. He had enough measurements to do the tomography calculations. He set to work on them with his calculator.

The result showed that the blobs were ovoid. Not cylinders, not spherical. Were the lines wires? No, they seemed to clump together at the ends like spiderwebs. Were they even real or artifacts of his calculation? He wished he had an industrial tomograph. Then he could produce a high-resolution tomogram. He didn't have the time or the facilities for that. But he wasn't unhappy with the results. He had vision into the inside of the device. Even his run-in with Wilson couldn't dim that elation.

He made a final drawing, one with perspective, and filed it in his lockbox.

John had his first inkling of the inside of the device, and now he would continue to dig at it until all the mysteries were solved. The answers were still far, far away, but he had some hope that he would one day discover them.

CHAPTER 25

Henry wrote out a note and taped it on the lab bay door: "Pinball Machine Moved to Woodman's." Then they managed to drag-carry the thing to the loading dock, where they maneuvered it into Henry's truck.

"Note this down," John said. " 'Add wheels.' "

"And let's make the next one out of plastic," Grace said.

It barely fit.

"It's going to fall out the back," Grace said, and she proceeded to wrap a hundred yards of red rope around the machine and the truck.

"Relax, Grace," Henry said as he started the truck.

"I'm riding in back with it," she squeaked, climbing in.

"Fine."

John followed in the Trans Am.

They unloaded the machine onto the street, and Grace stayed with it while Henry and John parked. Then they wrestled it into the back room, complicated by the three steps that connected the room to the bar area. Luckily, the bartender was there, a hefty fellow named Lou, and he helped get it up the steps.

"Can I try it out?" Lou asked.

"Sure. We just have to get it set up," John said, getting his level out. "We need to prop that side up."

Henry slid a shim under the leg nearest him. "How's that?" He wrote something in his notebook. "We should build screw levels right into the legs. There's no telling what kind of floor these things are going to be on."

"That's level." John took the gaming sticker out of his pocket and stuck it to the gla.s.s. "I think it's ready. Plug it in. Grace, do the honors."