Amaia measures the painting and four centimetres are missing

"Ninety-six point four."

"Again?"

"Three times, Tomás. With the steel tape and with the cloth one. Ninety-six point four high by a hundred and twenty-eight wide."

"And the record card says."

"The 1953 card says a hundred point four by a hundred and twenty-eight. Same width. Four centimetres more in height."

Tomás Elgueta dropped the folder onto the tool trolley and rubbed his eyes. In the conservation studio it was twenty to four in the morning.

"Amaia, the exhibition truck leaves at eight. At nine I close the inventory. If you put a measurement in the condition report that doesn't match the card, 'The Supper at Bethany' becomes a non-conforming item and it stays here."

"I know."

"And if it stays here, the loan falls through, and if the loan falls through, they'll have me for breakfast at the audit, because I'm the one who's kept the register for eleven years."

"I know that too."

"Then write a hundred point four and let's go to bed."

"No."

"Amaia."

"It's just that if I sign a hundred point four…" She stopped. "It gets copied, Tomás. It gets copied and nobody ever looks again. It's been copying itself since 1953."

"In 1953 it was right."

"In 1953 it was right, yes. And something happened between 1953 and now. It's twenty to four: we have time to find out what."

"We have four hours and twenty minutes."

"You have four hours and twenty minutes. I have a truck."

Tomás picked the folder up again.

"All right. A canvas can shrink."

"A canvas tightens and slackens with the humidity. Half a centimetre, one centimetre in a bad case. Not four. And not four only in height, leaving the width nailed at a hundred and twenty-eight."

"And if the card is wrong?"

"It could be. But look at it: it was written by someone who measured carefully, because they wrote down the decimals. A hundred point four. Someone inventing a measurement writes a hundred."

"Fine. And the edge?"

"That's where I was going. Come here."

They went over to the easel. Amaia switched on the raking light — the one you set almost parallel to the canvas, so that any relief throws a shadow — and lowered the lamp.

"Look at the top edge. See the line of little holes?"

"I see nail holes."

"They're from the first stretching, when the cloth was mounted on the stretcher in the seventeenth century. They're where they ought to be: three millimetres from the edge. Now look at the bottom."

"Hang on, I can't… Bring the light up a bit."

"Like that."

"There isn't a single one."

"Not a single one. The bottom edge has modern staples and nothing else. This canvas was cut along the bottom and re-stretched over a shorter stretcher, and whoever did it worked well: you can't see it from the front."

"When?"

"That's not my department. The archive is yours."

Tomás looked at his watch and sighed.

"Ten past four."

"The archive is in the basement, Tomás."

"I know where the archive is."

Downstairs, Tomás pulled three grey boxes off the historic-loans shelf and set them on the table.

"Arranged by year. How far back are we looking?"

"From 1953."

"There's everything in here, Amaia. Loans, restorations, building works, a priest's claim from 1970 about a carving that wasn't his…"

"Loans. Loans only. If something odd happens to a painting, it happens when it goes out of the door."

"So 1953 onwards. Here: 1958, diocesan exhibition, never left the building. 1960, nothing. 1961…"

"1961 what?"

"Hold on. 'Temporary loan to the cultural hall of the Arcedo Savings Bank, fifth centenary of the town.'"

"Did it go?"

"It went. Out on 14 June 1961, returned on 30 September. The loan is signed by the director, Práxedes Nieto."

"What else is in the folder?"

"A transport docket. An insurance receipt. And an invoice."

"Read it."

"'Aniceto Roldán, frames and mouldings, 4 Herrería Street.' Date, 20 June 1961. Item: 'For adaptation of the work to the hall's frame. Trimming of stretcher and canvas, lower side, four centimetres. Re-stretching and tacking. One hundred and eighty pesetas.'"

Tomás laid the invoice on the table. They both read it again from the top.

"Four centimetres," he said. "For a hundred and eighty pesetas."

"They trimmed it so it would fit a frame the savings bank already owned."

"And then they gave it back."

"And when it came back nobody measured it. Why would they, if the measurement was already written down."

"Sixty-five years."

"Sixty-five years dragging along a figure that stopped being true one Tuesday in June."

Tomás didn't answer. He was turning pages.

"There's something else in here. An envelope."

"Sealed?"

"Folded. It says '1961. B.' in pencil."

"Open it. Carefully, from the edge."

Inside the envelope was a strip of canvas about four centimetres high and a hundred and twenty-eight long, folded three times, its varnish darkened and its weave intact. Amaia spread it on the blotting paper with both hands and went very still.

"Tomás."

"What."

"Bring me the magnifier. The one with the black handle."

"What can you see?"

"Bring me the magnifier."

He brought it. Amaia pulled the desk lamp down until it almost grazed the paper and laid it flat, aimed at the right-hand corner of the strip, where the paint was still paint and not tacking edge.

"There are letters."

"A signature?"

"Half a signature. The other half went with the trimming of the stretcher, or it's under the varnish. It reads 'ez', then an f with a full stop, then a year."

"What year?"

"Sixteen thirty-one."

"That painting has been catalogued as anonymous since 1953."

"Because in 1953 the signature was no longer on the painting. It was in here."

"So Roldán, the frame man, cut off the signature."

"Roldán cut four centimetres off a painting he'd been told to adapt and charged a hundred and eighty pesetas. He probably never even saw it. But somebody did see it, Tomás. Somebody kept the strip. Nobody folds a strip of canvas in three and puts it in an envelope by accident."

"There's a note here. Behind the envelope. Same handwriting as the loan."

"Read it."

"'I am keeping the strip. It bears a signature and a date. I have not managed to convince anyone to have it sewn back on. Let whoever comes after see it. P. Nieto, 2 October 1961.'"

Tomás put the note on the table, next to the invoice, and said nothing for a long while.

"We're whoever comes after."

"We're whoever comes after, sixty-five years late."

"Amaia, I can't write 'the signature turned up' in a condition report. I'm nobody to attribute a seventeenth-century painting."

"Neither am I. And we're not going to. The report gets what we measured and what we found: real height ninety-six point four, discrepancy documented against the 1953 card, cause established by Aniceto Roldán's invoice of 20 June 1961, and an original strip of canvas with a fragmentary signature and date, kept in the file by Práxedes Nieto. Whoever is entitled to say the name can say it, with a laboratory and an archive. We supply the fact."

"That I can sign."

"That's the only thing we can sign."

Tomás sat down on the stool and looked at the strip, still spread out on the blotter.

"You know what makes me angriest? That Nieto wrote it down. He wrote it down and filed it, in his box, in his year. It's been two metres from my desk since the day I started working here."

"Two metres from mine as well, if that's any comfort."

"It isn't."

"No."

"Eleven years keeping this register, and what's going to stay with me longest is opening an envelope in the basement of my own archive."

"Put that in the note, then."

"You can't put that in a discrepancy note."

"I know."

Tomás stood up and gathered the folder.

"I'm going to draft the discrepancy note, with the invoice scanned and Nieto's note. And then I'll call the insurers, who will be delighted to hear from me at seven in the morning."

"And the truck?" said Amaia.

"The truck," said Tomás, "I don't know. It depends how long the insurers take to revalue a piece that has changed its measurements and possibly its author in the same night."

"I sign at seven," said Amaia. "With the strip inside, in its envelope, and with Nieto's name in the report. If the insurers don't make it in time, the truck goes on Monday; the painting is going to carry on measuring ninety-six point four either way."