“The Pipe and Passage?” said Sameer. “That sounds like a gentlemen’s club. Full of tobacco smoke and secret entrances.”

“It sounds obscene, yeah,” said Toby the ginger. He made a motion to show how “pipe and passage” could be construed smuttily. Diantha gave him a glance that made him fold inward.

They spent days debating and Googling and whispering the words “Pipe and Passage” to one another, with no idea what they could mean. Diantha seemed impatient, as though she was waiting for someone else to figure out the meaning, so she wasn’t forced to be messenger and interpreter both. At last, on Friday after lights-out, Diantha took a drag on a clove cigarette and announced she had the answer.

“Pipe,” it turned out, referred to the Great Siberian Natural Gas Pipeline. And “Passage” referred to the Great Northern Shipping Passage. They were both the brainchildren of Lamar Tucker (a Texan who had helped pioneer slickwater fracking) in partnership with a Russian conglomerate called Vilkitskiy Shipping. The Russians wanted a new shipping route to replace the Northwest Passage, one that avoided Canada altogether, going through the heart of the Arctic ice. There was just one catch: Their route went straight through a massive deposit of ancient methane clathrate in the Chukchi Sea that had been trapped under the ice for millions of years. Scientists warned that releasing all that methane at once could supercharge the effects of climate change overnight. Hence the pipeline—Tucker believed you could drill down by inches, release the pressure slowly, and trap the still-frozen methane by bonding it with silicates. Then you could pipe the energy-rich methane sludge to a facility in Yakutsk. You’d generate enough electricity to power half of eastern Russia, and maybe sell surplus power to Mongolia, China, or even Japan.

“But it’s going to go wrong, I know it,” said Diantha. “They have no idea what they’re tampering with. They must be stopped.”

“Yes,” said Patricia. “But what are we supposed to do?”

“Do?” said Diantha. “Look around. We are the best students at Eltisley Maze. Between all of us, we have mastered so many skills. Toby, I have seen you unmelt the last snows of spring, and reverse three days’ decay. Sameer, you once tricked a bank manager into giving you five hundred pounds and the power of invisibility. Patricia, I have heard the teachers whisper that you have a connection to nature that even they don’t fully understand. We can do this. The Tree depends on us.”

They set off that very night, with only what they could carry. Diantha insisted: There could be no dallying (and no chance for anybody to have a change of heart and tell the teachers). They all went back to their rooms at Eltisley Hall and stuffed random objects into duffel bags.

“Where are we even going?” Toby said. “I have a practical in two days. At Eltisley, where they expect you to show up.”