By the fourth Friday, people on the Green had started reading the back of the paper first too. Danya saw them do it. The baker turned the sheet over before she read the price of bread. Beto's mother turned it over before she read the lost cats. It made Danya feel proud and nervous at the same time, which he had not known you could feel at once.

This week the back page had a picture of an old radio, the big wooden kind with a round speaker like a face. Lightning bolts came out of it. Underneath it said:

On the night before Halloween in 1938, a radio play about Martians landing on Earth was so realistic that the whole country panicked. Millions of people fled their homes, the roads were jammed, and nobody could tell it was only a play.

And beside it, on the Honest Page, in neat black capitals: TRUE.

"Four," said Danya. "Four weeks in a row."

"Let me listen first," said Tara.

Tara was fifteen. She sat on the bench by the notice board most evenings with a book she was not really reading, listening to whatever was going on around her. She listened longer than anyone Danya knew. Sometimes she listened so long that the conversation ended before she said anything at all.

"Listen to what?" said Danya.

"The story," said Tara. "Read it to me. Slowly."

Danya read it out loud. Tara listened with her eyes on the grass.

"Hm," she said, when he finished.

"What?"

"It says nobody could tell it was a play," said Tara. "That's a big thing to say. About a whole country."

"Who checked that?" said Danya. "That's what I want to know."

"Can I say one thing?"

"Go on."

"I was going to say," said Tara slowly, "that you sound like you've already decided it's wrong."

Danya opened his mouth. Then he shut it.

"Maybe," he said.

"Then let's find out properly," said Tara. "Let me listen first."

The printer did not even look up this time.

"Box," she said.

The slip was there, under a note about a missing bicycle bell.

Radio panic. Mark it True. My grandad remembers it.

No name. Pencil first, and then ink over it, every letter.

Danya held it up to the window. Tara held out a hand for the slip, and Danya passed it over. Tara did not hold it to the light. She turned it over and ran her thumb over the back.

"I think we missed someone," she said.

"Who?"

"Not who. What." Tara gave him the slip again, back side up. "Feel the back."

Danya felt it. The paper was smooth everywhere except in one place, where the letters had pushed through so hard that they stood up on the back like a tiny bit of braille. He turned it over. The raised place was under one word: True.

"They pressed hardest on True," said Tara. "In the pencil and in the ink. Like they really wanted it to be."

"Same person," said Danya. "Four weeks. And they want it to be true."

"Or they believe it," said Tara. "That's different."

"Says who?"

"Hm." Tara smiled. "Says me, for now. You'll check."

The big book on the back table was open at a page with the same old radio, and a little drawing of a long silver machine on three tall legs, striding over a farmhouse.

The Martians, said the heading.

"My grandad remembers it," said Danya, reading the slip again. "Whose grandad? It was 1938. That would have to be a very old grandad."

"Hm," said Tara. She was looking at the drawing of the machine.

Danya bent over the page.

The hammer rang once. A spark jumped off the anvil and did not go out. It waited. They followed.

The spark came in under the print shop door with a crackle, like a radio being tuned. It hopped once onto the old radio in the picture, and then went to the green curtain and waited.

The spark slid under the green curtain into the drying room, and the drying room went back much further than the shop did.

Tara went in slowly, the way she did everything. Danya went in after her.

The corridor was full of sound this time. Not loud, but everywhere: the hiss and pop of radio static, coming from nowhere in particular. Pages hung overhead as always. Along the walls, between the doors, were rows of old wooden radios, all switched on, all tuned to nothing.

"Where did they get it from?" said a voice through the static.

Trace was leaning against a radio with his notebook out.

"Danya," he said. "And you're new."

"Tara," said Tara. "I'm listening."

"Good," said Trace. "That's half of it in this corridor. Keep going back, and keep your ears open. Where did they get it from? We'll follow the radio."

Claim was sitting on a stool beside a radio, with her red pencil behind her ear and a pot of glue at her feet. She had turned the radio off, and the space around her was the only quiet place in the corridor.

"What exactly does it say?" she said.

Danya read it out. Claim held up one paw and counted.

"Say the claim in one sentence," she said.

"A radio play made everybody panic. Says the paper," said Danya.

"Everybody," said Claim. "Underline the exact words. How many things does the paper say happened?"

Danya wrote them out on a strip, one per line.

1. In 1938 there was a radio play about Martians landing.

2. Nobody could tell it was only a play.

3. Millions of people panicked and fled their homes.

4. The whole country.

"Four claims," said Claim. "Any of them could be true, and the others not. Which one is the story?"

Danya looked at them. The play was just a fact. People made radio plays all the time. The part everybody told was the running.

"Three and four," he said. "The millions. The whole country."

"Underline the exact words," said Claim. "Whole country. Twice."

Danya did. Tara watched the red line go across.

"Can I say one thing?" said Tara.

"Always," said Claim. "What exactly is it?"

"Hm. I was going to say the paper doesn't say who," said Tara. "It just says everybody. 'The whole country' is a lot of people to ask. Nobody could ask them all."

"What exactly does it say? Somebody said 'whole country' without asking them all," said Claim. "Go and find out who."

The first doors were full of the radio night. There was a film poster with screaming people. A comic book. A museum display with a mannequin in a hat clutching a radio. Then, quite soon, a door with a card that said 31 October 1938, the very next day.

Inside, the room was papered from floor to ceiling with newspapers. Headlines in thick black letters, one on top of another.

RADIO LISTENERS IN PANIC.

TERROR BY RADIO.

FAKE RADIO WAR STIRS TERROR THROUGH U.S.

There were hundreds of them. More arrived as they watched, sliding down from the ceiling and settling over the others, like snow.

Danya felt his heart lift. He knew what to do here. Three weeks of drying room had taught him.

"How long after did they say it?" he said, before anyone else could. "The next day. The very next morning. These were written by people who were there, the same night. That's the best witness there is. They're not two hundred years off. They're one day off."

He turned to Tara, pleased. "So it really happened. Mark it True."

"Who was there?" said a slow voice.

An old bear with round glasses and a long blue scarf was sitting on the edge of an old printing press in the middle of the room. He had a newspaper folded on his knee.

"Weigh," said Danya. "They were there. They wrote it the next day."

"Weigh it. Don't count it," said Weigh. "How quick a witness is, is one thing. But ask another question too. What did the teller have to gain?"

"Gain?"

Weigh unfolded the newspaper on his knee. On the inside page was a short piece about money, and radio, and advertising.

"In those years," said Weigh, "radio was new, and it was taking the advertising money that used to go to newspapers. Newspapers were losing money to radio. And here was a night when radio frightened people."

Danya stared at the wall of headlines.

"So the papers wanted radio to look bad," he said slowly.

"Weigh it. I didn't say they lied," said Weigh. "I said they had a reason to tell it big. A quick witness can still have a reason to stretch. Twelve and a half thousand articles in three weeks. That is a lot of articles for a paper that wants its readers back."

Danya's face was hot. He had been so sure. He had used his own rule, the one that had worked three weeks in a row, and it had walked him straight into a wall.

"I counted the days," he said. "I didn't ask why they were telling it."

"You asked a good question," said Tara quietly. "You just stopped at one."

"Keep going back," said Trace. "Not to the next morning. To the night itself. Who wrote it down first? What did the radio actually say?"

He led them to a door with a card that said 30 October 1938, 8 p.m. Inside was a single old radio on a table, and beside it, in a thick folder, the script of the play.

Trace turned the pages. "Check the date. This is the play," he said. "Every word they read out. Look here, at the very start."

At the top of the first page, before any Martians, there was an announcement. It said that this was a play, made from a novel called The War of the Worlds.

"It said so," said Danya.

"Keep going back through it," said Trace. He turned to the middle. "Here. At the break. And here, after the break. And here, at the end." He tapped four places. "Four times, the radio said it was a play."

"Then why did anybody believe it?" said Danya.

"Let me listen first," said Tara. She put her ear to the old radio. It was playing, very quietly, from somewhere in the middle. A man's voice was describing something huge rising out of a field. There was dance music before it and dance music after it, and in between, news bulletins, one after another, as if real news were interrupting a real dance band.

Tara listened for a long time. Nobody hurried her.

"I think we missed someone," she said at last.

"Who?"

"The people who turned it on in the middle," said Tara. "If you switched on late, you missed the first announcement. You'd just hear the news bulletins. They sound real. Some of those people might have been frightened."

"So some people were frightened," said Danya.

"Some," said Tara. "Not the whole country. Some. And I still think we missed someone."

Danya put his ear to the radio too. The voice was describing a crowd at the edge of a field, and a hissing sound, and a light. Then there was a scream, and the sound cut off, and there was nothing but static for a long time. Then a calm voice said something about the next bulletin.

He found he was holding his breath.

"It's good," he said, surprised. "It's really good. If I'd switched on in the middle, I might have been scared too."

"Let me listen first," said Tara, and kept listening.

"Is the music real?" said Danya.

"Hm. I think it's part of the play," said Tara. "That's the clever bit. A dance band, then news, then the dance band again. That's how real news sounded then. So it sounds real because it's shaped like real."

"Who checked that?" said Danya.

"Nobody, yet," said Tara. "I'm only listening. You check."

Trace was writing it down already. "Keep going back," he said. "Who wrote it down first? The script says the band and the bulletins were written for the play. Every word."

"So it was a play shaped like the news," said Danya. "And it said four times that it was a play."

"Both," said Tara. "Both can be true. That's why it's hard."

"Who, though?" said Danya.

"The listeners," said Tara. "All the papers are about the listeners. But nobody in this room is a listener. Where are they?"

"Who was there?" said Weigh, from the doorway. He sounded pleased.

"The people with their radios on," said Tara. "That night. They're the ones who were there. Did anybody ask them?"

Trace had already gone. He came back a minute later with a thin printed sheet.

"Somebody asked," he said. "That very night. A man called C. E. Hooper ran a company that phoned people to ask what they were listening to, so the radio stations knew which programmes were popular. He did it every week. That night his people called five thousand homes."

"And?"

"Check the date: that same night. Two homes in every hundred," said Trace, "were listening to the Martian play. The rest were listening to something else, or nothing at all."

Danya did the sum in his notebook. Two in every hundred, out of five thousand. "A hundred homes," he said. "A hundred out of five thousand."

"Weigh it," said Weigh. "That survey is only one way of counting. It doesn't tell you who was frightened. But it tells you something the headlines didn't. Most people weren't listening at all."

"You can't panic at a play you didn't hear," said Tara.

"So 'the whole country' is stretched," said Danya.

"A good witness can still be a long way off, and that one is stretched a long way," said Weigh.

"Keep going back, but there's one more room," said Trace. "Two years later. And it's the famous one."

The door had a card that said 1940. Inside was a thick book with a plain cover: The Invasion from Mars. A card beside it said it was by Hadley Cantril, a professor at Princeton University, who had studied that night.

"Check the date," said Trace. "Two years after. He sent people to ask listeners questions, and he worked out some big numbers."

He read from the card. Cantril had estimated that about six million people heard the play. He had estimated that about one million seven hundred thousand thought it was real news. And he had estimated that about one million two hundred thousand were frightened or disturbed.

"That's a lot," said Danya. "That's more than a million."

"How many is that out of six million?" said Weigh.

Danya wrote it out. 1.2 million out of 6 million. He made both numbers ten times bigger to get rid of the point, and divided. 12 out of 60. "One in five," he said. "Twenty in every hundred who heard it."

"And Hooper said two in every hundred homes were listening at all," said Tara. "Those don't fit very well."

"No, they don't," said Weigh. "Weigh them both. Don't count them."

Trace turned to a door off to one side, with a much newer card: 2013.

"Seventy-five years later," he said. "Two historians, Jefferson Pooley and Michael Socolow, went back to all of it. The papers, the surveys, Cantril's book."

Danya did the sum. 2013 take away 1938. "Seventy-five years," he said.

"They wrote that Cantril's estimate of how many people heard it was more than twice as high as any other estimate at the time," said Trace. "And that the great panic, all over the country, didn't happen anything like the way the papers said."

Danya sat down on the floor. The static hissed in the corridor outside.

"So some people were frightened," he said. "Some people phoned the police. Some people maybe ran outside. And then the papers made it the whole country."

"Underline the exact words: some, or everybody? And then the story kept growing," said Claim, who had come in with her glue pot. "Fell, or hit? Some people, or everybody? Those are different claims."

Tara had been quiet for a long time, even for Tara.

"Can I say one thing?" she said.

Everybody waited.

"The note said, My grandad remembers it." Tara looked at Danya. "Somebody's grandad might really remember it. Maybe he was frightened. That could be true."

"Who was there? A grandad could have been. That could be true," said Weigh.

"So the person who wrote the note isn't lying either," said Tara. "They've got a real story. It's just a small one. And they've put it on top of a big one."

Danya thought about that.

"So were the papers lying?" he said.

"Did they think it was true?" said Weigh.

"Some of them. Probably."

"Then mostly they weren't lying," said Weigh. "They had a few real stories, and a reason to tell them big, and a public who liked a big story. People like a better story. That's how a few frightened households become a whole country running."

"Stretching is honest," said Trace, "when you say that you did it."

"The papers didn't say," said Danya.

"No," said Trace. "So you will."

Danya looked at his four claims. One. The play: true. Two. Nobody could tell it was a play: the play said so four times. Three. Millions fled: stretched. Four. The whole country: stretched a very long way. And underneath it all, a question that would not go away.

"How many, then?" he said. "How many were really frightened?"

"Nobody knows," said Weigh. "The best counts don't agree, and nobody counted at the time. That's allowed."

He wrote it out on a clean page.

From the Real World — a correction.

On 30 October 1938 the CBS radio network broadcast a play of The War of the Worlds. TRUE.

Nobody could tell it was a play. STRETCHED. The broadcast said four times that it was a play. People who tuned in late could miss that.

Some listeners were frightened, and some telephoned the police. TRUE.

Millions fled and the whole country panicked. STRETCHED. A ratings survey that night found 2 homes in 100 listening. The next day's papers, which were losing advertising to radio, told it much bigger.

How many people were frightened. NOBODY KNOWS. The best estimates disagree.

He showed it to Claim. She underlined some twice and nodded.

He showed it to Trace. Trace checked the dates against his notebook. "Yes," he said. "That's the night, not the morning after. Good."

He showed it to Weigh. Weigh read it twice.

"Weighed," he said. "Not counted. And this time you asked what the teller had to gain."

Tara read it last. She read it slowly, the way she listened.

"You put the grandad in," she said. "Some listeners were frightened."

"He might be one of them," said Danya.

At the bottom, in pencil, he wrote a last small line: Ask someone who remembers a big night on the radio or the TV. What did they hear? What did the papers say? Then he inked over the pencil, the way he always did now, so the printer could read it.

On the inside of the cover, under FELL, DROPPED and EUREKA, he wrote a fourth word: PANIC.

The spark slid back under the curtain, and the drying room was just a cupboard again.

The print shop was quiet. No static. The big book lay open at the striding silver machine.

The printer read the correction. She read it twice.

"Four weeks," she said. "This one's different. You've been hard on the papers."

"The papers were in it," said Danya. "They had a reason to tell it big."

The printer looked at her press, and at the stack of Friday Papers beside it, and was quiet for a moment.

"So do I, sometimes," she said. "Every paper does. Good. Print it."

"And the note?" said Tara. "The one pressed hard on True?"

"Still no name," said the printer. "But somebody really wants these to be true. I'd like to know who, too."

The spark dimmed to a warm dot and settled back on the anvil. The Green was just the Green again.

Back on the Green

Danya and Tara sat on the bench by the notice board while the light went. The radio in the Whetstone's window was playing dance music, the old kind.

"You were quiet in there," said Danya.

"I was listening," said Tara.

"You found the listeners. I'd never have found the listeners. I was too busy counting days."

Tara shrugged. "You found the papers," she said. "I'd have believed the papers. They were so quick."

They sat for a while.

"Can I say one thing?" said Tara.

"You always say that. And then you always say something good."

"I was going to say," said Tara, "that you were sure about the papers before you checked. For about a minute. You were sure because your rule had worked three times."

Danya did not say anything for a long time.

"Yes," he said at last. "I was."

He took out his notebook and looked at his four words. Then he turned to a blank page at the back and wrote, in pencil, very small: Check my own rules too.

He looked at it. He did not ink over it. He left that one in pencil.