The next day after school, Will and Chester resumed their work at the excavation. Will was returning from dumping the spoils, his wheelbarrow stacked high with empty buckets as he trundled to the end of the tunnel where Chester was hacking away at the stone layer.

"How's it going?" Will asked him.

"It's not getting any easier, that's for sure," Chester replied, wiping the sweat from his forehead with a dirty sleeve and smearing dirt across his face in the process.

"Hang on, let me have a look. You take a break."

"OK."

Will shone his helmet lamp over the rock surface, the subtle browns and yellows of the strata gouged randomly by the tip of the pickax, and sighed loudly. "I think we'd better stop and think about this for a minute. No point in banging our heads on a sandstone wall! Let's have a drink."

"Yeah, good idea," Chester said gratefully.

They went into the main chamber, where Will handed Chester a bottle of water.

"Glad you wanted to do some more of this. It's pretty addictive, isn't it?" he said to Chester, who was staring into the middle distance.

Chester looked at him. "Well, yes and no, really. I said I'd help you get through the rock, but after that I'm not so sure. My arms really hurt last night."

"Oh, you'll get used to it and, besides, you're a natural."

"You think so? Really?" Chester beamed.

"No doubt about it. You could be nearly as good as me one day!"

Chester punched him playfully on the arm and they laughed, but their laughter petered out as Will's expression turned serious.

"What is it?" Chester asked.

"We're going to have to rethink this. The sandstone vein might just be too thick for us to get through." Will knitted his fingers together and rested his hands on top of his head, an affectation he had picked up from his father. "How do you feel about… about going under it?"

"Under it? Won't that take us too deep?"

"Nah, I've gone deeper before."

"When?"

"A couple of my tunnels went much farther down than this," Will said evasively. "You see, if we dig under it, we can use the sandstone, because it's a solid layer, for the roof of the new tunnel. Probably won't even need to use any props."

"No props?" Chester said.

"It'll be perfectly safe."

"What if it isn't? What if it collapses with us underneath?" Chester looked distinctly unhappy.

"You worry too much. Come on, let's get on with it!" Will had already made up his mind and was starting off down the tunnel when Chester called after him.

"Hey, why are we breaking our backs on this… I mean, is there anything on any of the blueprints? What's the point?"

Will was quite taken aback by the question, and it was several seconds before he replied. "No, there's nothing marked on the ordnance surveys or Dad's archive maps," he admitted. He took a deep breath and turned to Chester. "The digging is the point."

"So you think there's something buried there?" Chester asked quickly. "Like the stuff in those old garbage dumps you were talking about?"

Will shook his head. "No. Of course the finds are great, but this is far more important." He swept his hand extravagantly in front of him.

"What is?"

"All this!" Will ran his eyes over the sides of the tunnel and then the roof above them. "Don't you feel it? With every shovelful, it's like we're traveling back in time." He paused, smiling to himself. "Where no one has gone for centuries… or maybe never gone before."

"So you've no idea what's there?" Chester asked.

"Absolutely none, but I'm not about to let a bit of sandstone beat me," Will replied resolutely.

Chester was still flummoxed. "It's just… I was thinking if we aren't heading for anything in particular, why don't we just work on the other tunnel?"

Will shook his head again but offered no further explanation…

"But it would be so much easier," Chester said, a tone of exasperation creeping into his voice as if he knew he wasn't going to get a sensible answer out of Will. "Why not?"

"A hunch," Will said abruptly and was off down the tunnel before Chester could utter another word. He shrugged and reached for his pickax.

"He's crazy. And I must be crazy, too. What on earth am I doing here?" he mumbled to himself. "Could be at home, right now… on the PlayStation… and warm and dry." He looked down at his mud-sodden clothes. "Crazy, crazy, crazy!" he repeated several times.

Dr. Burrows's day had been the same as usual. He was reclining luxuriously in the dentist's chair with a newspaper folded in his lap, on the brink of slipping into his post-lunchtime nap, when the door of the museum burst open. Joe Carruthers, former major, strode purposefully in and scanned the room until he located Dr. Burrows, whose head was lolling drowsily in the dentist's chair.

"Look sharp, Burrows!" he bellowed, almost taking pleasure in Dr. Burrows's reaction as his head jerked up. Joe Carruthers, a veteran of the Second World War, had never lost his military bearing or his brusqueness. Dr. Burrows had given him the rather unkind nickname "Pineapple Joe" because of his strikingly red and bulbous nose — possibly the result of a war injury or, as Dr. Burrows sometimes speculated, more likely due to his consumption of excessive amounts of gin. He was surprisingly sprightly for a man in his seventies and tended to bark loudly. He was the last person Dr. Burrows wanted to see right now.

"Saddle up, Burrows, need you to come and have a look at something for me, if you can spare a mo'? Course you can, see you're not busy here, are you?

"Ah, no, sorry Mr. Carruthers, I can't leave the museum unattended. I'm on duty, after all," Dr. Burrows said sluggishly, reluctantly abandoning the last vestiges of sleep.

Joe Carruthers continued to bellow at him from across the museum hall. "Come on, man, this is a special duty, y'know. Want your opinion. My daughter and her new hubby bought a house just off Main Street. Been having work done on the kitchen and they found something… something funny."

"Funny in what way?" Dr. Burrows asked, still irked by the intrusion.

"Funny hole in the floor."

"Isn't that something for the builders to deal with?"

"Not that sort of thing, old man. Not that sort of thing at all."

"Why?" Dr. Burrows asked, his curiosity roused.

"Better if you come and have a gander for yourself, old chap. I mean, you know all about the history hereabouts. Thought of you immediately. Best man for the job, I told my Penny. This chappie really knows his stuff, I said to her."

Dr. Burrows rather relished the idea that he was regarded as the local historical expert, so he got to his feet and self-importantly put on his jacket. Having locked up the museum, he fell into step beside Pineapple Joe's forced march along Main Street, and they soon turned onto Jekyll Street. Pineapple Joe spoke only once as they turned another corner, into Marrineau Square.

"Those darn dogs — people shouldn't let them run wild like that," he grumbled as he squinted at some papers blowing across the road in the distance. "Should be kept on a leash." They arrived at the house.

Number 23 was a terraced house, no different from all the others that lined the four sides of square, built of brick with typical early Georgian features. Although each property was rather narrow, with just a thin sliver of garden at the rear, Dr. Burrows had admired them on the occasions he'd happened to be in the area and welcomed the chance to have a look inside one.

Pineapple Joe hammered on the original four-paneled Georgian door with enough force to cave it in, Dr. Burrows wincing with each blow. A young woman answered the door, her face lighting up at the sight of her father.