Idoia climbs to the roof and the flue is split

Previously: an avalanche sealed nine people inside the Iratxeta refuge. Sabino Amantegui, warden until 2022, admitted he had drawn off sixty litres of diesel.

Seven days of diesel were left at Iratxeta on the sixth day, and five of the nine woke up with a headache.

Lena Bouzas, forty-one, climber and anaesthetist, put it on the table at a quarter past seven, with the generator still running and the dining room at twelve degrees. She said it the way these things get said once they have been thought about a great deal: without raising her voice, and with a list.

"Me, since Thursday. Aitor, yesterday mid-afternoon. Mercedes has had a headache and nausea for two days and has been calling it her hip. Casimiro fell asleep sitting up at eleven in the morning the day before yesterday, which is a very odd hour to fall asleep. And Sabino, who nobody asks anything because we all assume it's the hypothermia."

"We're at six below and eating out of tins," said Ramiro Bouzas, forty-four, boat carpenter, Lena's brother. "My head hurts too."

"It does. But yours goes away when you go down to the woodstore for kindling, and you're the one who told me so on Friday."

Idoia Bergara, warden of the refuge and an A&E nurse until 2019, set her mug down on the long table and did not answer straight away. In A&E she had seen three times what Lena was describing without naming it: a whole family with headaches, a grandfather asleep at the wrong hour, everyone better in the street and worse at home.

"Say it in full, Lena."

"Carbon monoxide. A gas that comes off anything that burns badly and smells of nothing at all. If it were flu, it wouldn't lift the moment you go down to the woodstore. If it were the cold, it would be hitting all nine of us, not five."

Mercedes Arriaga, a retired justice of the peace who has kept the fuel accounts on the inside back cover of the signing-in book since the third day, closed the book with her finger inside it.

"And why five and not nine?"

"Because of where each of us sleeps," said Lena. "Me, on the top bunk in the small dormitory. Sabino, on the bottom one since the third day. Aitor, on the other bunk along that same wall. Mercedes and Casimiro, on the west benches. All five of us in the half of the house that backs onto the generator room."

Idoia went down to the generator room with the battery lamp and Ramiro behind her. She switched the engine off at half past seven, a full hour early, and the building was left with the sound snow makes when there is no other.

The Iratxeta generator is a single-cylinder diesel bolted to a concrete bed, with an exhaust pipe that climbs flush against the wall, crosses the floor slab and comes out above the stone roof, on the windward side, with a cowl so the snow cannot get in. It was fitted in 2009 and the club inspects it every second autumn.

Idoia ran her hand along the pipe from the engine elbow to the point where it enters the ceiling. It was hot, as it should be.

"Soot on the elbow, the usual," she said. "But no soot on the floor, no black mark on the wall, no blown joint in sight."

"Nothing down here," said Ramiro. "And if there were a leak in this stretch, this room would be a gas chamber and you and I would already be on the floor."

"Then it's up there."

They went back to the dining room with half an answer, which is the worst way to come back. Fani Quiroga, a twenty-eight-year-old geologist who had come up to Iratxeta to change the sensors on the slope, came down with her instrument case open on the table.

"I've got a data logger with three channels," she said. "Temperature, humidity and an electrochemical carbon monoxide sensor on the same board, because slope sensors are calibrated in a hut and there you do need it. I don't know whether the monoxide channel has any battery left, and I won't know until I switch it on."

"Switch it on."

"It'll take a while. That board needs twenty minutes to settle and then a good hour before the curve says anything. If I give you a number sooner, I'll be giving you noise."

Idoia looked at her watch, wrote the time in the red-covered notebook and went up to the high dormitory, which is the room you leave for the roof from, through a wooden hatch seventy centimetres square.

Txomin Elordi, sixty-two, a shepherd who has carried the club's post up to Iratxeta since 1994, followed her up the stairs and stopped beneath the hatch.

"The avalanche swept the north face and the high west side," he said. "The east pitch was left loaded but whole. If you step on it, step along the line of the thick slates, the ones that bear on the beam."

"Will it take one person?"

"One. Not two."

Idoia tied herself to the dormitory beam with an eight-millimetre rope that Ramiro passed round her waist, put on her mountain boots and opened the hatch at twenty to nine. The cold came in all at once, and so did something she was not expecting: a smell. Not a strong smell. A lukewarm one, of engine, of a garage with the shutter down.

"It smells of exhaust," she said, with half her body outside.

"Carbon monoxide has no smell," Lena called from below.

"Monoxide doesn't. But an exhaust carries other things in it, and those do smell."

The Iratxeta roof is slate laid on timber beams, with a short pitch and two faces. Snow covered the whole of it except for a metre and a half strip beside the generator's flue, where the crust was grey and sunken, melted and frozen again several times over. Idoia knelt at the edge of that strip before going any closer, because that grey patch was where you could see that something had been coming out hot, for days, where it should not.

She pushed the snow aside with her forearm until she reached the cowl. The cowl was in place, upright, undented, and nothing at all was coming out of it.

She put her hand underneath, between the slate and the pipe, and brought it out black.

The exhaust pipe was split exactly where it crosses the stone, on the underside, hidden beneath the overlap of the slate. It was not a hairline crack: it was a clean cut round half the circumference, the edges turned outward and the metal flattened on top. Anyone looking at the roof from the path would see a perfect cowl. Anyone who climbed up and put a hand on it, as she had just done, would find that the generator's smoke had spent six days coming out under the slates, working its way into the cavity between the stone and the floor slab, and dropping from there into the western half of the house through the same gaps the cables run through.

Idoia stayed up there five minutes with her black hand flat on the slate. Then she came down, closed the hatch and sat on the bench opposite Sabino Amantegui, sixty-six, warden of that refuge from 1991 to 2022, who had spent three days saying only what he had to and who that morning was sitting up, with the survival blanket folded over his knees.

She asked him nothing. She showed him the palm of her hand.

Sabino looked at it for as long as it takes a man to stop keeping something to himself.

"Under the slate," he said. "In the overlap, on the east side."

"How do you know?"

"Because that pipe goes through the stone with no sleeve. It was put in like that in 2009 and it was put in badly. It expands hot, it shrinks cold, and the stone doesn't forgive: it works against the metal every time the engine starts and every time it stops. I saw it open a finger's width in the autumn of 2021, I plugged it with refractory filler and I told the club. With snow on top and the engine running four hours a day, that finishes splitting."

Mercedes had opened the book and was writing without looking up.

"You came up on Tuesday at twenty to seven," said Idoia. "Before dawn, with the snow forecast already out. What did you come up for?"

"To warn you." Sabino ran a hand over six days of beard. "Forty centimetres fell on Sunday and it froze on Monday. I'd been waiting two winters for that combination and I knew what it would do to the pipe. I came up to tell the warden, which is you, and to plug it again if you let me."

"You didn't say a word to me."

"I signed at twenty to seven, I heard the eight of you in the kitchen and I went into the generator room by the landing door. Before knocking on your door I wanted to look at the starter, and the elbow of the pipe was black with fresh soot. After that I didn't need to go up on the roof to know: it was open."

"The three jerrycans," said Mercedes. "Let's go to the part he wouldn't tell us yesterday."

Sabino looked at Idoia and not at the magistrate.

"You had two hundred and forty litres and a sum worked out to burn them over twelve days, four hours a day. I had a plate, a pair of tin snips and two clamps in my rucksack, and a roof you weren't going to let me climb without arguing about it for half a morning, because I haven't been the warden of this house for three years. So I took three days off the tank before eight and poured in the sixty litres of water so the dipstick would keep reading nine. I meant to give them back that same afternoon, with the pipe wrapped, and tell you the whole thing together."

"You took three days of heat off us," said Ramiro.

"I took three days of smoke off you." Sabino propped himself on his elbow. "And then I stayed in the woodstore waiting for it to ease off, because you don't walk on wet slate in a blizzard. At seventeen minutes past ten the avalanche came down and caught me in there, with two metres of snow between that roof and me."

Lena Bouzas got up from the bench slowly, like someone who has been doing a sum for a while and does not like the answer.

"Sabino. Ten hours twenty over the first four days and three hours twelve yesterday. Thirteen hours and thirty-two minutes of engine with that pipe open, and us sleeping underneath it. Tell me how much we've breathed."