“Earthquake!” Carmen shouted.

Grady looked at his feet.

“She’s talking about the riddle, Grady.” Lizzie stifled a laugh as she hopped over a boulder that was half-blocking the path.

“It can be felt, but not seen. It destroys, but you can’t destroy it.” Carmen nodded smugly. “I am on a roll.”

Will hummed. “Not a bad suggestion, but we should keep thinking.” He paused and looked at the map. “We leave the coastal path here – we have to go this way.” He pointed towards the moorland.

“At least it should get us out of this wind.” Lizzie shivered. “It’s freezing.”

“The sun’s warm.” Grady turned his face to the sky. “We just need to get off the clifftop.”

I pulled out my binoculars, wiped the wet lenses, and held them to my eyes. When I had adjusted the focus, an expanse of moorland came closer. A lake glimmered ahead. We would be walking alongside it in less than an hour. “I see another team.” I pointed at a cluster of trees.

“Proves we’re going the right way.” Carmen grinned.

“If that’s team eight, they’re more than twenty minutes ahead of us,” Grady said as he handed a bag of pear drops around. “We’re losing time already.”

If it’s team eight.” I put a sweet in my mouth. “For all we know, that’s team one and we’re catching up.”

Lizzie nodded. “We just have to keep going – no second-guessing ourselves.”

“For five million pounds, we could pick up the pace,” Carmen suggested.

“OK.” Lizzie tightened her rucksack. “Who’s up for a run?”

Grady put his sweets away and we sped over the moor, feet pounding on the grass, kicking up clumps of mud and grunting with the weight of our equipment.

The ground passed in a blur under my feet; I trampled flowers, thistles and oatmeal-coloured grass. Soon we were jogging beside a rushing stream and I couldn’t resist. I paused, kneeled and splashed water on my face, cooling off.

Lizzie saw me and held up her hand. “Quick break, guys?”

Carmen flopped down beside me and drank from her bottle. She allowed her head to tip back when she was done, her pale throat open to the sky. Lizzie filled her own bottle from the stream and added a water purification tablet.

“You don’t think this water’s pure enough already?” I raised my eyebrows. The stream was as clear as a screen.

Lizzie snorted. “Even with my glasses I can’t see bacteria, can you?”

“Guess not.” I smiled as she put the bottle back in her rucksack and copied me, splashing her face and hands. Droplets clung to her wrists, which seemed fragile and delicate, like the bare veins of an autumn leaf.

An otter was a dark flash and gone, winding sinuously between the rocks and speeding away from us upstream.

“You know … they fill the water at home … with special chemicals to feminize men?” Grady gasped as he took a drink. “That’s why there’re hardly any protests against the government these days – not enough … testosterone in the population.”

Lizzie shook her head with a smile. “How’re you getting on with that rucksack, Grady?” she asked. “Is this pace all right for you?”

“I’ll manage.” He put his hands on his knees.

“We’re making good time.” She checked her watch. “It’s not sunset for a while yet. We might even get to the third checkpoint today – what do you think?”

Will stood a little apart, waiting for us to get running again. He tapped his useless watch. “Five million pounds?” he said.

Lizzie leaped up. “Show me where we’re heading.”

Will pointed to the map, then off into the distance. “See that lake?” Maybe three-quarters of a mile away the lake shimmered. “That’s where we’re going.”

By the time Will was four, Mum didn’t have many friends left – only a couple of diehards from when she had me: Auntie Ros and Auntie Anne.

I remember the last play date I had with my best friend, Matthew. Auntie Anne was pregnant with Matthew’s little sister. Will walked up to her, cocked his head to one side and asked, “Is there a baby inside your tummy?”

Auntie Anne nodded. “Yes, there is, Will. You were inside your mummy’s tummy once too.”

Will looked at her for a long time. Then he walked away without saying anything. Auntie Anne smiled at Mum, and Matthew and I carried on playing with my trains.

The next thing I knew, Auntie Anne was screaming. Will had wandered back up to her holding a thick hardback book and hit her across the stomach as hard as he could.

The whole time, the thoughtful expression never left his face.

“I can’t do this any more, Carrie.” Auntie Anne hustled Matthew away, sobbing and clutching her belly. “He’s out of control. You’ve created a monster – you never tell him off, never punish him. If you let this carry on, what’s he going to be like when he gets to school?”

The last thing she said as she propelled a shocked Matthew out of the door was that he wasn’t going to be able to see me again.

Mum cuddled Will for an hour after that. No one seemed to care that my best friend was gone.

By the time we were nearing the lake, we had all slowed to a jog.

“I need to get fitter,” Carmen gasped as she staggered to a halt.

“We’ll walk for a while.” Lizzie wiped her steamed glasses on her sleeve. “But we should keep up a good pace, at least until we reach the trees.” She kept her feet moving, jogging on the spot.

Grady was barely able to speak. He put his hands on his knees and wobbled.

Dios, Grady, are you having a heart attack?” Carmen stared.

Grady held up a hand. “I’m … all right.”

“Five million pounds is all very well –” I patted Grady on the shoulder – “but we don’t want to kill Grady.”

“Wait a minute!” Carmen rushed to a patch of grass sheltered by a leaning rock. Mushrooms clustered beneath the overhang. “Check these out.”

“Don’t pick wild mushrooms, Car.” I rolled my shoulders. “Could be poisonous.”

“These aren’t poisonous, chico.” Carmen bent and picked three. “Don’t you recognize them?”

Will leaned close to her hand. “Psilocybin mushrooms.”

“That’s right – magic mushrooms. A little for each of us.”

“Are you kidding?” But Lizzie’s eyes had brightened with humour. “We have to stay focused.”

“Just a tiny bit, chica, enough so all this running becomes fun. You promised me fun.” Carmen was already lifting the shiny brown top to her lips.

“I don’t think you should, Car.” I frowned. “If that is poisonous—”

“It isn’t.” Will’s eyes were on Carmen’s mouth now.

“But what if it is?” I insisted. “We have no way to call for help. Some mushrooms are lethal.”

“Let me see.” Grady had got his breath back and he pulled Carmen’s hand closer to him and squinted. “It does look like the pictures Dad made me memorize. And I do have this.” He patted the pocket of his rucksack that contained his medical kit. “I can at least induce vomiting.”

“If she poisons herself, she’ll already be vomiting.” I glared.

“I’m taking it.” Carmen bit the mushroom. “If I’m still OK in five minutes, you can take some too.”

Carmen!” Lizzie cried. But she swallowed and there was nothing any of us could do.

We stared at her in horrified fascination. Nothing happened. Nothing continued to happen.

“See, I’m fine.” Carmen laughed. “Give me half an hour and the fun should kick in. Then I can run again.”

“Or you’ll be falling over a lot,” I muttered.

Carmen wrapped her mushrooms and put them in her jacket pocket, then we all started to hike around the lake towards the trees.

“It’s really beautiful here, isn’t it?” Lizzie murmured as she strode beside me. Her nose piercing sparkled in the same light that caught the lake, and her hair stood up in wild, wind-blown spikes.

I nodded. “In a desolate way.”

The lake lapped the shore beside us. I allowed my hand to brush against hers and she leaned slightly towards me. At least, I thought she did. Internally I was at war – sometimes I wondered if I should push things between us before she went to university and someone else got there first. Most times I knew I’d be ruining everything if I did. She was my best friend.

She tensed up in the way that told me she had something to say.

I sighed. “Spit it out.”

“You’re really going to give up your future to keep an eye on Will?”

I opened my mouth, but she kept going.

“At least tell me that once Will graduates, you’ll try again with civil engineering? If we win, you could use your money to pay your tuition fees – you wouldn’t have to rely on your mum.”

I closed my eyes briefly. “I don’t know, Lizzie. I don’t want to be three or four years older than everyone else on the course and … what if Will decides to do a PhD or something?”

“Haven’t you heard of mature students?” Lizzie hit me with her cap. “This has been your dream for three years, Ben. And it’s important. You could be doing some real good in the world. Can’t you plan a cut-off point? Like, when Will is eighteen you’ve done your time.”

“It’s not prison, Liz. I—”

Grady gave a shout. “There’s another team!”

They were approaching the trees from a different direction around the coast and it looked like they would reach cover before us.

“Hey, Will, d’you think they went to the wrong coordinates?” I called.

Will gave his lopsided smirk. “Looks like it.”

A girl walked in front with a very long black ponytail. Her skin was brown and she was slim and long-legged. Her rucksack was bright purple. There was a smaller girl on her team and a boy who looked like her twin – or brother, at least. Two larger guys marched alongside the younger girl like personal bodyguards, one dark-skinned, one light.

“Could be team one,” I said. “Prisha something, wasn’t it?”

“And they’re not much ahead of us.” Lizzie grinned. “That’s excellent.”

She called over to Carmen. “How are you feeling?”

Carmen was staring at the water, her head on one side, mouth slightly open.

“Car?”

“It’s so pretty. You guys need to try this. Look at the sparkles.”

I laughed.

Lizzie took Carmen’s arm. “C’mon, babe – we’re walking.”

Carmen giggled. “Your voice sounds like bells.”

Lizzie laughed. “Can you run?”

Carmen shambled happily into a jog. Lizzie guided her towards Will.

You keep an eye on her.”

Will lifted his head from the map. “Dreamer-says-what?”

You said she could take the mushrooms,” Lizzie snapped. “So you’re in charge.”

“I’m reading the map.”

“We can all read a map,” I said. “Give it to Grady.”

Carmen started to sing as she ran. “Grady, Grady, give me your answer do…” Then she forgot the rest of the song and switched to a Spanish lullaby. “Din dan, din don dan, campanitas sonarán…”

When she finished her song, she quietly translated the final verse. “Close your eyes and go to sleep, because the night is coming soon.” She paused. “Din, don, dan.”

Will sped up to catch her.

“I’m tempted,” Lizzie whispered. “She’s definitely having the most fun.”

I looked at Will and grinned. He was already frustrated with preventing her from wandering off.

I watched for a moment as Will slid his arm around Carmen’s waist, under her rucksack. He looked back at me and our eyes met. Then he smiled and turned his attention back to guiding Carmen. He was fine.

I squeezed Lizzie’s shoulder. “I do want that million pounds. You’re right, I can do the course later and what’s left could be seed money for important projects, once I’ve got some experience under my belt.”

She smiled at me. “I’m so pleased, Ben. I’m not sure you’d be you if you weren’t planning to save at least a bit of the world.”

“We’re going to have to leave the lake and head for the trees,” Grady said, flapping the map importantly. “There’s quite a dip ahead; I think we should go around.”

“Will?” I couldn’t help checking.

Will looked up from Carmen and nodded. “That was my plan.”

“See.” Grady sniffed.

“OK, sorry.”

We stepped out in the direction Grady pointed and Carmen started to sing again. An old song and a favourite of Lizzie’s. Lizzie joined in, her voice higher than Carmen’s. Grady hesitated and then he too started to sing. Will met my eye.

I grinned. “Run to the rock, rock won’t you hide me…”

We were all singing loudly as we jogged across the moor towards the first leaning copse of rowan, long-trunked and red-berried. Birches clustered behind them, silver-grey. The ground underfoot became boggier, making it more difficult to maintain the pace, but Carmen’s singing kept going.

“Did you know,” Grady’s voice raised above the singing, “Paul McCartney has been dead for years? He was replaced by a lookalike in 1966.”