"You've found the holiday pictures?" Victor was already out of his chair and heading around the coffee table. Charlotte slid beside Em on the other side.

"Yip." He waited until Victor was settled beside him. "That's us at the cottage." He pressed the FORWARD button, and the photograph slid stylishly to one side to reveal an out-of-focus picture of a mountain split by a bar on the left-hand side. "Mum must have tried to take that from the car. I don't know where it is." He thumbed the button again, and the screen transformed to a shot of a Labrador flopped sleepily in the doorway of a country pub. "We had lunch there a couple of times." Then the main street of Kenmare . . . then a view of a lake in a valley that might have been taken from a helicopter but was actually shot from high up on a mountain road . . . then forests on the Ring of Kerry . . . then boats in a harbor . . . The final one was a picture of the ferry in Rosslare, its decks rain-swept by a sudden squall.

Em looked up at Victor and frowned. "That's it. That's all the holiday pictures I remember us taking." He glanced back at the camera screen again. The icon on the bottom right was a filled triangle. If there were no pictures left, the triangle would be empty. "Wait a minute." Em pressed the button again.

The photograph was in sharp focus, with no sign of shaking, as if the camera had been attached to a tripod when it was taken. It showed a wooden table, but not one Em remembered from the holiday. On the tabletop was a vase of wilting flowers. Beside them was an assortment of objects: a cup and saucer, a scrap of paper, an open fountain pen with its cap set neatly beside its nib, a small china ornament of a sleeping cat, an open notebook, and a box of matches. It looked for all the world like the cartoon for a still life painting arranged by an artist with neither taste nor talent.

It was the scrap of paper that drew Em's eyes like a magnet. Charlotte spotted it at much the same time, for she reached across to point and murmur "Look at that!" Even on the tiny screen what was drawn on the paper was evident. It was the same symbol Em had seen in the clinic where his mother was a prisoner, the same symbol Victor had shown him on the back of the one-dollar bill: the eye within the triangle used as a sign by the Knights of Themis.

Victor bent over to take a closer look. "This is what he wanted you to see," he said with certainty. "This is the message your father sent you."

Em stared at the scrappily planned still life in bewilderment. "I don't get it."

"Neither do I," Victor admitted. "Not yet." He stood up. "Does this camera have a standard computer connection?"

"I think so."

Victor made for the door. "We need to take a closer look at that picture."

Victor's laptop was one of the new MacBooks. A bar crawled swiftly across the screen as Victor downloaded the entire camera content. In a moment, the whole of his laptop screen was filled with Kenmare's main street. Victor tapped a key, and they were looking at the mystery still life. The eye in the triangle stared back at them balefully.

"He's written in the notebook," Charlotte said at once.

Em followed her gaze. On the tiny camera screen, the open notebook had displayed what looked like an empty page with faint ruled lines. Now, on the laptop, it was evident that each line supported a message in the tiniest example of Professor Goverton's cramped, neat handwriting Em had ever seen. Even with the larger screen, it was impossible to read what it said. "Can you zoom in?"

Victor was already tapping keys. "Think so."

The screen zoomed, blurred, then cleared to pin-sharp focus. At the top were the words CURRENT READING, followed by the professor's translation of the lost Nostradamus prophecy. The remainder of the notebook page was filled with what looked like a random series of numbers, which meant nothing to Em at all. He scanned the first line: 12 6 9 8 3 6 57 1 2 10 4 7 13 34 6 (53 15 3-4) 197 2 9.

"I don't understand," Em said. "Do you?"

"Secret message?" Charlotte suggested.

Frowning, Victor said, "Obviously a secret message-Em's eyes only. Looks like a cipher of some sort." He hesitated. "Or possibly a code."

"Aren't they the same thing?" Em asked.

Victor shook his head. "A cipher substitutes something for each letter of the alphabet. A code substitutes something for every word of the secret message. This is almost bound to be a cipher."

Em felt as if he was trapped by Victor's gaze. The iPod had been engraved with a message. The one about good listening. Maybe there was more engraving on it somewhere else; they hadn't really searched. Or maybe if he listened to every song, one of them would be interrupted by his father saying, The key to your cipher is A equals three. Em swallowed. "Maybe there was something else on the iPod."

"Yes," Victor said slowly. "I was wondering about that myself. But the iPod's gone missing, almost certainly into the hands of the Knights. So our friends on the other side could easily have the key." He shrugged suddenly. "But so far we're the only ones who have the message, which puts us ahead."

Em didn't see how. "If they can't decipher the message without the message and we can't decipher the message without the key, that puts us about even, I'd say."

"Not quite," Victor said. "If we just had the key, there's no way on God's sweet earth we could guess the message. But since we have the message, there's a chance I might be able to crack it without the key."

"You could do that?" Em asked. He was beginning to think his luck had taken a real upturn the day he met Victor.

"Probably. Ciphers were part of my basic training. But the real question isn't whether I can do it; it's whether I can do it in a reasonable time. My guess is, we don't have a month or two to work on this one."

"It could take a month?" Charlotte put in.

Victor sniffed. "It could take a year. Depends on how complicated Em's father made the cipher. I'm hoping he didn't use a computer to create it. That could really slow us down."

Em felt just the smallest swelling of relief. "Dad was a Luddite," he said. "There's no way he would have used a computer."

"That could be a help," Victor said. He turned back to the laptop and pulled a notebook and ballpoint from his pocket. "Okay, the first thing to find out is whether or not this actually is a cipher. After that we can worry about what it means."

"How do you do that?" Em asked curiously. "Find out whether it really is a cipher?

"Frequency analysis," Victor said without raising his head from the screen. "On average, every letter of the alphabet appears with a given frequency in any piece of text. E is the most frequent-turns up nearly thirteen percent of the time. T is the next most frequent, then A, then O, then I. Your father seems to be substituting numbers for letters in this cipher, so if I find a number that appears more often than any other, it's likely to stand for E. After that I look for T, then maybe A and work out their actual frequency in relation to the whole message. If the percentages stack up, that means we're definitely dealing with a cipher."

"Won't that let you decipher the message?" Charlotte asked at once.

"Possibly. Depends on how sophisticated Em's father was in setting it up. For the moment I want to confirm that we're dealing with a cipher. Now, do you think you could manage to shut up for five minutes and let me get to work?"

In fact it took him nearly ten, and Em knew they were in trouble from the depth of his frown. Eventually he threw down his ballpoint. "It's not a cipher," he announced.

"Are you sure?"

"Of course I'm bloody sure!" Victor responded angrily. "He must have created a code. Which means he must have sent you the key in advance."

"In the iPod?" Em asked.

Victor nodded. "Probably."

"In which case-" Em began.

"We're dead," Victor finished for him. "I'm not saying codes can't be broken, but without the key it's going to take far longer than I think we have available. Especially since I can't send it to our experts in the Section. But there's no way I'm going to risk that." He knuckled his eyes tiredly.

"Maybe he didn't send the key in the iPod," Charlotte suggested.

Victor looked at her. "Go on."

"Maybe the clue's in the camera."

"We went through all the pictures in the camera."

"No you didn't," Charlotte told him. "You went through the holiday file, because that's what he told Em to do. 'Remember our last family holiday . . .' But you didn't go through pictures in any other file."

"You're right," Victor muttered. He pushed the camera toward Em. "Have a look. You work it better than I can."

Em shook his head. "You've downloaded everything onto your laptop. If there's anything else, it'll be on there already."

Victor nodded, then pushed his finger across the trackpad and began to tap keys.

Em leaned across to watch. There were two more files of photographs apart from the holiday pictures they'd already examined. One seemed to be more holiday shots, although not one featuring people. On the third one Em suddenly realized what he was looking at. "That's the Nostradamus Museum," he said excitedly. "Dad must have taken these on one of his French trips to research his book."

"Okay," Victor said, "let's examine each one of these carefully. If there's a Nostradamus connection, it might well be where he hid the key."

That made sense to Em, but even though they examined every picture in the file minutely, there was nothing that would help them with the message. Victor brought up the second file, only to discover that it was a series of old woodcuts. He paged through them slowly, but none showed any sign of additions or tampering. "I think those may have been for a presentation to his history students," Em said.

Victor turned away from the computer. "We're missing something," he said. "We need to put ourselves into your father's head. He has a vital message he needs to communicate to you; but he can't afford to have it read by the wrong people, so he hides it carefully away and writes it in code. But at the same time he has to make sure you read it, so the code has to be easy for you to crack. Which means either you already have the key and don't know it. Or . . ." He frowned thoughtfully. ". . . or the key is contained in the message itself! That could be it." He brought up the notebook page again and pushed the laptop toward Em. "Have another look at those numbers and see if any of them rings a bell. A birthday or some significant date-that sort of thing.

Em stared at the figures, then shook his head. "No."

"Come on!" Victor exclaimed impatiently. "Really try. There has to be something in there."

Em looked again. The figures remained figures, just a series of numbers without logic or pattern. "I wonder what 'current reading' means?" he said.

Victor blinked. "What?"

"He wrote 'current reading' at the top," Em said. "I just wondered what that meant."

"It's a book code," Charlotte said suddenly.

"Presumably it's a reference to some book he was-" Victor stopped, his mouth open. "What did you just say?"

"It's a book code," Charlotte repeated. "I saw something about them in a movie once."

Victor stared at her for a long moment, then abruptly thumped himself on the forehead. "My God, how could I have been so stupid? Of course! I must be going senile."

"You know how he made up the code?" Em frowned as he looked from one to the other.

"Of course I do!" Victor said. "Well, I do now, thanks to Charlotte. So obvious. A book code takes time to set up, but once you've done it, it's absolutely unbreakable without the key. But you can pass on the key very easily. If it's somebody you know, you can even pass it in such a way that it would mean nothing to anybody who intercepted it."

"So are you going to keep me in suspense?" Em asked him. "Or is one of you going to tell me what a book code is?"

Victor grinned. "Simple. I want to send you a secret message that nobody else could possibly decode. So the first thing we do is agree between us on the book that will be the key. It's quite a good idea to pick something fairly big, like the Bible or the complete works of Shakespeare; but the actual book doesn't matter so long as we both have a copy. I then compose my message using words taken from the book we agreed on. But instead of sending you the message itself, I send you the exact location of where each word appears in the book. Page number, followed by line number, followed by position in the line-word number three or four or whatever. All you do to reconstruct the message is follow my instructions using your own copy of the book."

"What happens if somebody else has a copy of the book? Couldn't they just look up the words as well?"

Victor gave him a withering look. "They don't know which book we agreed on, do they?"

Em hesitated. "But Dad and I didn't agree on any book," he protested. "We never talked about sending messages in code."

"Maybe not, but he sent you the clue right along with the message. 'Current reading.' We know he must have composed the message sometime after he got ill. All you have to do is remember what you were reading around that time. Maybe something you were set to study at school: Dickens or Chaucer or something. Something he would have noticed you reading at the time." He leaned forward eagerly. "Can you remember?"

Em remembered all right; and it wasn't Dickens or Chaucer. He felt his face begin to flush. "It was Harry Potter."

Chapter 33.

"Which one?" Victor asked. "Haven't read them myself, but I understand there's more than one."

"Harry Potter and the Goblet of Fire." Em's flush receded. Victor clearly didn't think there was anything much wrong with reading Harry Potter. "I missed it first time around."

"Big book?"

Em nodded. "More than six hundred pages."

"Perfect for a book code. Six hundred pages is a lot of words. Couple of hundred thousand by my reckoning. Well, well, well . . ." He grinned broadly at Em. "Don't suppose you have a copy with you?"

Em shook his head. "No way."

"Doesn't matter. There's a bookshop around the corner; I can slip out and buy one. Hardback or paperback?"

"They're both the same, aren't they?"

"Same text, but you sometimes get a variation in layout or type size. Can lead to different page numbers. Even a page or two difference is a nightmare when you're decoding. I'd rather we were all singing from the same hymn-sheet."

"It was the hardback," Em told him. "Mum bought me a copy."

Okay," Victor said, "I'll see if I can find us the hardback."

Em and Charlotte were paging through the holiday photographs on the laptop again when they heard Victor's key in the lock. Moments later Victor appeared in the living room waving a fat hardback with a skinny dragon on the jacket. "Got it!" he exclaimed triumphantly.

Em felt a tingle of excitement intermixed with a distinct undertone of fear. If Victor was right about the code-and Em didn't doubt for an instant that he was right-they would soon know what Em's father had been trying to tell him so secretly. That was dangerous knowledge. It would almost certainly call for dangerous action. "What do we do now?"

"We get to work on the code. Should be quick and easy if we go at it together."

"What do you want me to do?" Em asked. The fear racked up another notch, but he hid it successfully.

"You can do the book bit since you're the Potter fan. I'll call out the page numbers and so on from the picture on the computer. You find the word and call it out to me. Charlotte will write it down. We'll soon know what your father was trying to tell us."

It was an innocent enough phrase, but it got to Em a little. Dad wasn't trying to tell us anything-he was trying to tell me. He pushed the reaction down. It was stupid. Victor only meant that they were in this whole mess together; and, frankly, Em was glad of it. He knew with absolute certainty that he would never have gotten this far without Victor's help. Or Charlotte's. Actually, without their help, he would probably be a prisoner of the Knights by now. "Okay," he said, and held out his hand to take the book.

"Right," Victor said briskly as he leaned over the laptop, "turn to page twelve."

Em opened the book.

"Got it? Now count down to line six. You there?"

"Yes."

"Now the ninth word on that line . . . ?"

Em counted, using his forefinger to keep his place. "My," he said. "'There is a little more in the bottle, my Lord.' Ninth word is my."

Charlotte wrote it down as Victor consulted his laptop again. "Turn back to page eight," he instructed. "Sixth word in line three."