Fatboy stopped laughing and looked at them both a little strangely for a moment, then shook his head as if dismissing a fanciful idea. "Cool, kids." He took the envelope with a sweep of his hand and stood up. "See you, Becks. See you, little bro."

"If we win the six million, you promise you'll share it?" Tane asked one last time.

"If we win the six million, I'll eat my motorcycle helmet!" Fatboy was out the door, his final laugh echoing back in through the open window. Moo-ha-ha-ha. Moo-ha-ha-ha. Then the throaty roar of his bike and he was gone. Then the throaty roar of his bike and he was gone.

"He'll be honest," Rebecca said in a conciliatory way to Tane, who felt anything but conciliatory.

He nodded. "He'd better. But you're right. What else could we do? Imagine if the numbers come up and we haven't got a ticket!" He looked at her for a moment and she looked at him. Then, at exactly the same time, they both burst out laughing. It had nothing to do with Fatboy, Tane thought. It was just the sheer excitement of it all, and maybe a bit of relief at having finally solved the problem. the problem.

Now the new problem was how to fill in the time until the live televised Lotto draw at eight o'clock that evening. Tane looked at his watch. Only nine hours and forty-seven minutes to go.

He said, "Our share would be four million dollars. What could we buy with that?"

"A new house," Rebecca murmured, almost to herself. "But don't forget the SOS. There's more to this whole thing than getting rich. Whoever sent those numbers did so for a reason."

Tane stood up with a mischievous glint in his eye. "You'd better come see this."

Tane's computer was on in his bedroom. Rebecca sat on the bed while Tane took the chair and opened an Internet browser. She watched with a fascinated frown as he typed some numbers into the address bar.

202.27.216.195.

"Those are the numbers from the message...," she realized.

Tane nodded. "It's an IP address. We learned about those last year."

"An Internet address. Of course!" Rebecca actually smacked herself on the forehead like they do in cartoons. "I should have recognized the pattern. What Web site does it take us to?"

"Have a look."

She stood behind him as the page slowly loaded onto the screen. The first thing that came up was the bright blue NASA logo. The next was a series of letters that they both recognized: BATSE. Below that were Username and Pa.s.sword boxes. Tane carefully typed "guest" into the Username, and "Compton1" into the Pa.s.sword.

He said, "It took me a couple of goes to get it right, because it was case sensitive."

"You clever bunny," Rebecca breathed. "Is this what I think it is?"

Tane nodded. "All the BATSE data." He pointed at a list. "That's the one we got from Professor Barnes. And that one arrived yesterday. These are all the ones in between. Want to a.n.a.lyze them?"

"Wanna try and stop me!" She almost kicked him out of the chair.

A moment later, her program was whirring away.

"It'll be quicker this time," she said. "I reprogrammed it to look for the Morse code patterns. It's quite clever but also quite complex. Do you want to know..."

"I-"

She didn't give him time to answer. "I went back and examined the raw data, and I found out something interesting. You see, the bursts are radiation waves, like an AM radio signal using amplitude modification to convey the ones and zeroes-"

"I'll take your word for it." Tane grinned.

"No, it's simple!" Rebecca said. "Imagine waves on a beach. There are big waves; those are ones. And there are little waves; those are zeroes."

"Okay." Tane nodded. "That much I understand."

"But sometimes there are gaps between the waves. And those are the gaps between the Morse code characters!"

"That is clever! And it'll make it much easier," Tane said. They had spent ages trying to work out all the possible combinations of the first message.

"Yeah, and faster..." She paused, noticing Tane's sly smile. "What are you smiling at?"

"I think I know who sent the message."

"You do?! Who?"

"Well, my guess is that was the final part of the message. Kind of like a signing off."

"TR?"

"Who do you know with the initials TR?"

Rebecca looked blank, and Tane's grin grew bigger.

"Isn't it obvious? TR. Tane and Rebecca. It's us. We sent the message to ourselves!"

Rebecca blinked rapidly a few times but said nothing as the enormity of that sank in.

Eventually she said, "Makes you wonder about the SOS, then, doesn't it."

Tane looked at his watch again. Nine hours and forty-three minutes to go.

SAt.u.r.dAY N NIGHT Tane's watch said twenty minutes to go, and he was sure the hands were standing still. But as he watched, the second hand inexorably flicked over. From where he was sitting, on the soft leather sofa in the middle lounge of his parents' house, the lights of the city blazed up into the clear night sky. The flashing lights of an airplane made a staccato string of pearls through the sky above the city. He barely noticed it. The second hand ticked over again. to go, and he was sure the hands were standing still. But as he watched, the second hand inexorably flicked over. From where he was sitting, on the soft leather sofa in the middle lounge of his parents' house, the lights of the city blazed up into the clear night sky. The flashing lights of an airplane made a staccato string of pearls through the sky above the city. He barely noticed it. The second hand ticked over again.

Rebecca's program had already decoded a second message from the future and was busy working on the third. The second message was just as cryptic as the first.

PROFVICGRNCHMRAPRJCTSTOPIT.BUYSUBEONTLS.DNTGOMST.DNTTLNE1.

Rebecca was clicking her fingers in front of Tane's face to get his attention.

"Concentrate," Rebecca said. "This is important."

Tane didn't think it was all that important, but it was taking Rebecca's mind off the last twenty minutes, so he tried to concentrate, for her sake.

It was hard. His hands were shaking and he wanted to vomit. If the numbers were right, then Rebecca would be able to pay all their bills, and they wouldn't have to move to Masterton. Everything would be all right.

"It's called the grandfather paradox, and it goes like this. What if you went back in time and killed your own grandfather?"

"Why?"

"Why what?"

"Why would I go back in time and kill Grandad? He's nice. I've got nothing against Grandad."

"Tane! Focus! That doesn't matter. We're just saying if. if. Okay. Okay. If If you went back in time and killed your grandfather when he was just a boy, then you would have never been born. Therefore, you could not have gone back in time to kill your grandfather. And so you would have been born, and so you could go back and kill him, but then you wouldn't have been born...and around and around it goes." you went back in time and killed your grandfather when he was just a boy, then you would have never been born. Therefore, you could not have gone back in time to kill your grandfather. And so you would have been born, and so you could go back and kill him, but then you wouldn't have been born...and around and around it goes."

"Grandad takes me fishing," Tane said, but quickly added, when he saw that he was about to get thumped, "But I get it, I get it!"

"Some people say that time is like a Mobius strip. An endless loop with no start, no end, and a single surface, called the present."

Tane just shook his head. This science stuff was elementary to Rebecca, but it was way beyond him. His watch said nineteen minutes to go. What if the numbers were wrong! What if they weren't Lotto numbers at all? What if the numbers were wrong! What if they weren't Lotto numbers at all?

"What's a Mobius strip?" he asked.

"Oh, come on! Do you ever stay awake in math?" Rebecca cried, and jumped up. She disappeared into Tane's room for a second and reemerged with paper, scissors, tape, and a pen. Tane watched intently as she cut a long strip from the paper and held the ends together in a loop.

"A Mobius strip is a piece of paper with only one side and one edge."

Tane tried to imagine that. "No way. If a piece of paper has a top, then it has to have a bottom. How can a piece of paper have only one side?"

"Watch."

Rebecca took one end of the strip of paper and twisted it over, just once. She taped it to the other end. "There you go. A piece of paper with only one side."

Tane took it and examined it. "Nope. Look, a top and a bottom. Or I suppose you'd say an inside and an outside." He knew he wasn't going to win this argument, but it was always fun to try.

Rebecca offered him the pen. "Draw a line longways, around the strip. Don't lift your pen off the surface. Stay on one side of the paper only."

Tane shook his head but took the pen and started drawing.

What if there was no Lotto win? No great scientific discovery? And Rebecca would still go to Masterton.

After a few seconds of drawing, he found himself right back where he started, joining up with the start of his line.

"So?"

"So you drew on only one side of the paper, right?"

"Yeah?" He looked at the Mobius strip. He had drawn around both the inside and the outside of the loop.

"See, it has only one side."

Tane frowned and forgot about his watch for the first time that day.

"But what has this got to do with us?"

"It's like we're on that loop. And when someone in the future sends a message to the past-"

"When we we send a message to ourselves..." send a message to ourselves..."

"Whoever. But it's like they have made a hole in the paper and pa.s.sed the message through to where we are in the past. But instead of paper, it's quantum foam, and the message is the gamma-ray burst."

"And what has my grandfather got to do with all this?"

"Well, they sent the Lotto numbers, right? But when we win-"

"If."

"Okay. Just suppose for a moment that it is us sending the messages."

"It is!" Tane insisted. "Think about it. Who else would know that we had thought of a.n.a.lyzing the BATSE data just at that precise time. Only us!"

"All right, us. If we win the Lotto but then forget to send the numbers to ourselves, then we won't win the Lotto, and around and around it goes!"

"Wow." Tane could think of nothing else to say, really.

Rebecca held up a notebook. "So I've got this notebook, and I have recorded the exact dates and times of the gamma-ray messages. Along with what the messages said, of course. Sometime in the future we have to send the messages, and any others that arrive, exactly as we received them. Otherwise, kaboom, kaboom, the grandfather paradox." the grandfather paradox."

"Leave my grandad out of this," Tane muttered. "And where are we even going to get the gamma-ray time-messaging-machine thingy from anyway?"

"That part I'm not sure of. In the meantime, let's see that new message again."

Rebecca opened the notebook and they pored over it together. Rebecca lightly drew some lines in pencil to separate what she thought were the words.

PROF VIC GRN CHMRA PRJCT STOP IT. BUY SUB EON TLS. DNT GO MST. DNT TL NE1

She said, "I think it's like text-messaging. That kind of truncated English."

Tane picked up the rest of the paper that Rebecca had made the Mobius strip from. "So what have we got?"

"I think the first part is easy. PROF VIC GRN PROF VIC GRN has to be Professor Vic Green. I don't know who he is, but we can Google him or check with the universities later." has to be Professor Vic Green. I don't know who he is, but we can Google him or check with the universities later."