With the arrival of December and no sightings of anything suspicious for many days, Fairnie gave permission for the cousins to return to school and for Jack to go home. Chloe and Jack celebrated by going Saturday shopping, while Itch realized he didn’t really have anywhere to go. Or anyone to go anywhere with. He had hoped to make some friends this term, but it hadn’t worked out like that. In fact, since returning from the military hospital he’d had even less contact with even fewer people.

The morning mail brought a parcel for Itch. All packages had to be inspected, and Kirsten had already opened it when she walked into the kitchen and passed it to Itch.

“Looks like your kind of thing, Itch—this your latest order?”

“Yup,” said Itch, and tipped out a small box containing some silvery crystals and a square of torn foil. Pointing at each in turn, he said, “That’s scandium and rhodium. And this …” He held up a clear packet containing a white powder. “It’s 52 on the Periodic Table. Come on then, Kirsten—you must have studied this at school. What’s this?”

“I could pretend to try and remember, but to be honest I don’t think I’ve ever known. Surprise me.”

“Tellurium,” said Itch, weighing the bag of powder in his hand. “Atomic weight 127.6, melting point 449.51 degrees Celsius. It’s not pure, unfortunately—sodium tellurite is the best I could do.” He put it down on the table, and saw her blank expression. “Well, you did ask.”

“How do you get all this stuff?” asked Kirsten.

“It’s difficult. Without Cake, and with all you guys around, there aren’t too many places. I’m having to restock my collection after … what happened … and I’m back up to forty elements now. Different collectors swap stuff, and some websites will sell to fifteen-year-olds. There’s a new art store opening in town apparently—they may be able to help.”

“An art store? What good is that?”

“Glazes, dyes—that kind of thing. Should be able to get some vanadium or something,” said Itch. “It would help if I could do eBay. You don’t fancy getting me some stuff, do you, Kirsten?”

“Yeah, that would go down well with the colonel!” she laughed.

On cue, Fairnie’s head appeared around the door. “What would go down well with me? You planning something, Itch?”

“I was thinking of this experiment. I’d love some iodine crystals and some concentrated ammonia really, but—”

“That’ll be a no, then,” interrupted Fairnie. “I remember enough of my chemistry, and that particular experiment ends in a bang. Correct?”

Itch fiddled with his packets and boxes. “It might…” He smiled. “Some other time maybe.”

“Not while I’m in charge.”

Itch gathered his new elements together. “Not even outside?”

“Especially outside. A large bang coming from the Lofte house is just not a good idea.”

“Yes, sir,” muttered Itch as he left the kitchen.

Kirsten and Fairnie watched him go. When they heard his bedroom door slam, Kirsten turned to Fairnie.

“Oh, Colonel, you know I said the smell in Lucy Cavendish’s room reminded me of something? Well, I’ve realized what it is.”

Fairnie raised an eyebrow.

“Itch’s bedroom smells exactly the same. Just thought I’d mention it.”

John Watkins had lived by the canal ever since he’d started teaching at the Cornwall Academy five years previously. There was a row of six fishermen’s cottages: four were second homes to London folk, and the fifth had its roof off, awaiting major repair work. His cottage was the last one before the dunes and the Atlantic, and he had fallen in love with it as soon as he saw it. When he wasn’t at school, the only place he wanted to be was here, by the sea.

That Sunday, nearing the end of a particularly windy and cold walk along the beach, Watkins recognized the familiar group escorting the cousins along the expanse of sand that the low tide had exposed: two agents leading the way, the cousins sixty-five feet behind them, and two more agents at the rear. Watkins knew that the van wouldn’t be far away; sure enough, looking back, he saw it in the parking lot near his cottage.

He waved, and as the Loftes realized who was approaching, they waved back. Watkins nodded his greeting to the security team as they passed him. Pulling his coat closer he shook hands with Itch, Jack, and Chloe, which seemed rather weird to them.

“Where are you heading?” he called over the noise of the wind. “You all look freezing!”

“We’re just escaping the house, sir. It can get a bit tense sometimes, particularly during a meal. We’re walking it off,” Itch told him.

“Of course, of course. Well, why don’t you all warm up at my place? I can offer you a hot drink.” He gestured to the four MI5 officers: Danny, Sam, Moz, and Kirsten.

“OK—thanks,” said Itch. He wasn’t actually sure about visiting teachers’ houses, even his homeroom teacher’s. But they were indeed frozen. “That’d be nice.”

“Excellent! Come on then!”

Moz and Kirsten secured the cottage; when they had given it the all-clear, the Loftes went in gratefully. Mr. Watkins dispensed hot tea and then passed around shortbread. The agents went back out with their drinks, eyes scanning the beach, minds still on the job. The Loftes were left alone with Mr. Watkins.

“This is weird,” said Chloe. “But nice weird,” she added quickly.

“Weird for me too,” said Watkins. “Don’t get many passersby at this time of year. But it’s nice to see you all.”

We weren’t exactly passing by, thought Itch; you came and got us. But he was happy to see where his teacher lived. The kitchen was all old wood cabinets and flooring, with a battered old stove. A pile of newspapers and magazines lay on one end of the table, and Itch idly took one from the top.

“Times Educational Supplement,” he read out loud. “Is this a magazine just for teachers?”

“Yes, it is indeed. I’ve read the TES for many years. You can borrow one if you want.”

Itch dropped it. “No thanks!”

Jack picked it up and started flicking through the pages.

“It’s where I saw the ad for the Cornwall Academy many years ago,” Mr. Watkins added. “Without it I might never have met you three.”

“Have you thought any more about what we were talking about at school the other day?” asked Itch.

“The security thing, you mean? No—forgive me, I haven’t. If one’s mind is made up, there really is no point in thinking anymore about it, is there?” Watkins stopped, noticing that Jack had gone rather pale. “What is it, Jack?” he asked.

She had pushed the magazine toward Itch and pointed to a brief article and photograph. He read it and felt the blood drain from his face.

The Mondo group of international hotels today announced the purchase of the Fitzherbert School in Brighton. The school, which was established in 1845, has been struggling to attract new pupils, and when the surprise offer was made to the governors last month, they felt they had to accept. The school will close at Christmas, and alternative places are being found for all existing pupils. A spokesman for Mondo Holdings said they would be demolishing the building and opening a five-star resort hotel on the site in two years’ time.

There was a small photo of the school from what looked like many decades ago. It looked cleaner and brighter, but still sent a chill through Itch; he passed the article to his homeroom teacher. While he was reading it, Chloe was looking between Jack and Itch.

“What is it? What’s happened?” she asked sharply. “Jack? Itch? One of you! What’s in the article?” Still no one spoke.

Watkins finished reading and put the magazine down. “It isn’t necessarily bad news,” he said eventually. “We have no idea who the Mondo group is, but they might just be who they say they are.”

Chloe reached over for it. “Well, as no one will tell me …” she said, and started reading. “The Fitzherbert School … Do we know it?”

“I used to teach there many moons ago,” said Watkins softly.

They were all waiting for Chloe to finish the article. Jack gave her a concerned look, but Itch shrugged. “I guess she’s going to have to know now,” he said.

Chloe had started to reread the article when it all fell into place. She looked at her brother, open-mouthed. “This is where you went, isn’t it? This is where you hid the rocks!”

By saying it out loud, it was as though a spell had been broken and Itch felt he had to tell Chloe everything that had happened after they left her at the mining school. He hadn’t really realized quite how much he had wanted to tell his sister the whole story, but now it came out in a torrent. Chloe and John Watkins listened in astonishment as Itch finished with the final flourish—that it had been his father who had rescued him.

“Dad? Are you kidding me?” Chloe was reeling.

Itch knew he was going to have to break his father’s confidence again. As he started to explain where Nicholas had been working these past few years, Watkins stood up and put his hands over his ears.

“No—I don’t need to know any of this. I’ve heard enough, thank you very much! I’ll put the kettle on again—don’t mind me.” He gathered up the mugs and retreated to the kitchen. The cousins heard him go outside and start up a conversation with the MI5 officers.

Itch continued to tell Chloe about their father. “But you can’t let him know I told you—he swore me to secrecy. I just think you deserve to know everything that we do, that’s all.”

“So he’s lied to us all this time. All the North Sea stuff, the troubles on the rig … all of it.”

“I think it’s for a good reason, Chloe. And if he hadn’t been in London when Mr. Watkins called, he’d never have been able to reach me down the well. So, all things considered …”

Chloe nodded as Mr. Watkins returned with more drinks.

“If you have quite finished talking about things I don’t need to know, I’ll come back in. So …” He sat down and looked at them.

Itch felt he was expected to say something. “OK, well, let’s assume these Mondo guys aren’t good people at all. So far, that’s been a safe bet where the rocks are concerned. Somehow they know about the 126 and intend to retrieve the rocks. If that’s the case, then it’s all over and I need to talk to Fairnie now.”

“I’ve just Googled Mondo: that company does run hotels around the world,” said Jack, showing her phone to Itch. “Barcelona, Los Angeles, Buenos Aires … They might be OK….”

“Might be.” Itch was thoughtful. “But it seems suspicious, don’t you think? School struggles for years—according to that article—then acquires some valuable rocks down the well, and all of a sudden they’re snapped up by a big company.”

“I agree it needs investigating further,” said Watkins. “Why don’t I call the school on Monday—I think I still know some of the staff down there—see what I can find out?”

Chloe looked relieved. “That sounds like a plan,” she said. “But then what? What happens next?”

“Why don’t you come to our homeroom after school on Monday, Chloe? Jack and Itch will be there last thing anyway, and I’ll fill you in on what I’ve learned,” Watkins suggested.

Itch was agitated now and pacing the room, frowning. “Can we wait that long? If Greencorps is behind the purchase of the school, we need to act now. If I tell Fairnie tonight, the school would be sealed off within hours.”

“And if it’s nothing?” said Mr. Watkins. “If it’s just a hotel company buying up an old building? What then?”

“I know, I know,” said Itch. “Then I might just as well have handed them over months ago.”This is my decision: they’re waiting for me on this, he thought. He sighed. “OK, let’s wait. But only until tomorrow. Then, if there’s anything you don’t like about what your friends at the Fitzherbert School are telling you, I’ll go to Fairnie.”

“Agreed,” said Jack.

Watkins nodded. “I’ll call as soon as I can on Monday. I might have to call from here just to keep things private.”

“We should get back,” said Jack, and they all stood up.

Moz and the team immediately came back in, ready to leave. Reverting to their previous formation, they marched out into the December gloom, calling their thanks to Watkins.

“Well, quite a gang, aren’t we?” Itch said.

When the walking expedition returned, it was dark, and Jude Lofte was preparing supper for whoever was in. The cousins sat around the kitchen table with steaming bowls of soup. Jack and Itch talked homework; Chloe was silent. The MI5 team was just filing out when Fairnie appeared at the door and they all trooped back in.

“We have a problem. I just spoke to Dr. Dart. She just received an email that appears to be from Shivvi; she’s threatening to burn the school down.”

There were sharp intakes of breath all around the kitchen. “And you were right about the cesium, Itch. The email is signed off with Cs + H₂O = a whole lot of fun.”

“Sounds like her,” he replied.

Fairnie looked at his team and nodded; they started to move, knowing what Fairnie was about to say. “We must find Shivvi. I’ll call the police for extra manpower. Let’s get to the school.”

The officers disappeared next door, and the colonel addressed the Lofte family. “Jack, you’re here tonight again. I need as many members of my team as possible on this one. I’ll call your parents. I don’t need to tell you what a chemical fire would mean. We have to assume that Shivvi has the cesium—and God knows what else. I’ll leave Danny here and the full house armor on—security shutters, cameras—everything. No one leaves. Clear?”

Chloe, Itch, and Jack nodded, and the colonel strode out of the kitchen.

Chloe and Itch spent the rest of the evening in Jack’s room at the top of the house.

“At least we’re safe here,” said Chloe, sitting on the floor with her back to the bed.

“Yes, ’cause it certainly doesn’t sound safe out there,” said Jack. “Would Mary—sorry, Shivvi—really burn the academy down, Itch?”

“Just what I was wondering,” said Itch. “We only knew Mary, not Shivvi, who caused the oil spillage and the deaths and went to jail. If she was planning to get the 126 through me, she failed—maybe she’s pretty pissed off. Who knows what she’s capable of?”

Jack had her laptop open. “Do you think we can Facebook people about this? Shouldn’t we warn them to stay inside or something?”

Itch shook his head. “No—that would be too public. We could text, though …”

And so Jack and Chloe spent the next few minutes texting friends a general warning, while Itch contacted Mr. Watkins.

After his visitors left, John Watkins had tidied up and settled down to prepare the next week’s lessons. Some classes were easing off for Christmas, but those with exams in the new year still needed plenty of attention, and he took a pile of the eleventh graders’ essays out of his bag. The house was warm, the tea freshly brewed, but the first essay on globalization was atrocious, and his attention wandered. His eyes were heavy and the armchair comfortable …

The next thing he knew was his heart racing as, nearby, a police siren wailed past. It was unusual to hear one at all—sometimes the summer tourists triggered a few, but in winter and this close, it was rare indeed. As he sat still, trying to clear his head, another siren joined the first, and Watkins knew that something serious was happening. He stood up and peered through his curtains, but the darkness in the garden and on the towpath was total.

But there was something else, he thought … and he stood uneasily by the window. The siren had certainly awakened him, but having lived on his own for so long, and knowing every creak and rattle of the old house, he knew it felt different. He stood motionless, his heart pounding again. He walked into the hall, and stood there too. He then peered into the room he used as his study; the light was off but the shadows in there looked different … wrong. Maybe he’d forgotten to draw the curtains. He stepped into the room and froze.

“Hello, sir.”

Watkins reeled around and, in the near dark, saw a small figure standing against the wall. “What the—!” He thumped the desk light on.

Shivvi stood by the bookcase, grinning, her hoodie pulled low over her face.

“Mary? What are you doing here? How dare you! I’ll—”

Shivvi produced a baseball bat from behind her back, and Watkins fell silent.

“As you know, my name isn’t Mary,” she said. “It’s Shivvi Tan Fook. Originally from Malaysia but not long out of the Ikoyi Prison in Lagos. That’s in Nigeria. But then, as a geography teacher, you’ll know all about that.” She pulled her hood back, her shaven head making her look even younger and smaller. Her smile, however, was not the easygoing glance of the teenager that Watkins had seen at the academy. This was a mean, cold grimace and she looked to him like a killer.