Toby was cinching the buckle on his canvas tool bag when the mountain moved.
It did not begin with a crack.
It began with a sound that Toby would describe later, in the quiet of his bedroom, as the sound a very old, very large tree makes in the final second before it falls — a deep, groaning exhalation from something enormous that has been holding its weight for a very long time and has simply run out of the ability to hold any longer.
Then the ceiling of the third-level western gallery came down.
The initial collapse was a single catastrophic structural failure: the hydraulic pressure of forty-seven tons of saturated upland topsoil, pine root material, and fractured limestone sheering through the primary ceiling mount that Thomas's beam inspection had identified as the weakest point.
The mount gave way with the sound of a cannon shot.
The oak beam above it folded, and the cascade of secondary failures took less than four seconds.
"Run for the cage!" Caleb screamed.
His voice was enormous and immediate in the enclosed gallery space, the kind of voice that bypasses rational thought entirely and moves directly to muscle.
Thomas was already moving, and Caleb's hand connected with his collar and propelled him forward through the expanding wall of grey dust toward the elevator shaft thirty yards away.
They made it through.
Behind them, the cascade of granite blocks, clay-packed rubble, and shattered oak timbers filled the western corridor in a solid, impenetrable wall.
In the rear alcove, Toby had thrown himself backward by pure reflex at the first sound of the ceiling mount giving way, landing hard against the rear granite wall of a small equipment recess five feet deep and four feet wide.
He had not chosen this spot.
His body had simply chosen the nearest available shelter with a solid roof and moved into it.
Pip hit the floor beside him at the same instant, spinning under Toby's legs and pressing against his shins.
The roar of the collapsing gallery lasted nine seconds.
When the sound ended, the silence it left behind was unlike any silence Toby had experienced before.
It was not quiet in the way that a room becomes quiet when conversation stops.
It was the silence of a space that had been removed from the rest of the world — sealed, muffled, encased in thirty feet of solid rock and clay on all sides.
Toby pressed his back against the granite wall of the alcove and took a slow, deliberate breath.
The air tasted of stone dust and wet clay.
His left elbow ached from the landing.
Pip was trembling against his boots, but he was breathing, and when Toby placed his hand on the terrier's flank, Pip immediately stopped shaking.
"All right, boy," Toby said, keeping his voice as level as he could manage.
"All right."
On the other side of the collapse barrier, Caleb scrambled to his feet in the elevator gallery and turned back toward the sealed corridor.
The wall of rubble stretched from floor to ceiling, perfectly solid, without a single gap large enough to pass a hand through.
He ran to it and put both palms flat against the jagged stone face.
"Toby!" he shouted.
"TOBY! Can you hear me?!"
The stone gave back nothing.
Thomas caught Caleb's arm and pulled him two steps backward, not from hopelessness but from experience.
"Stop," Thomas said firmly.
"Shouting through thirty feet of granite accomplishes nothing, Caleb."
"We go up, we get the surface crew organized, and we start a systematic extraction."
"He's an intelligent boy."
"If there's a survivable space back there, he will find a way to use it."
Caleb looked at Thomas for a long moment.
"He has a candle in his kit," he said, as much to himself as to the foreman.
"He always carries a backup candle."
"Then he has light," Thomas said.
"Now let's go get our boy out."
Caleb and Thomas reached the elevator cage at the same moment.
Thomas grabbed the signal rope and pulled it three times — the emergency evacuation code — sending a rapid series of bell strikes to the surface operator.
The cage motor engaged immediately.
From behind them, the sound that Toby would later describe as the tree-falling-sound reached them at the same instant that the limestone cap layer completed its structural failure.
The crack ran along the full sixty-foot length of the ceiling mount line in approximately one-third of a second, releasing the pent hydraulic energy of forty-seven tons of saturated overburden in a single continuous event.
Caleb had time to throw one arm across the elevator cage entrance and hold the door bar before the pressure wave of displaced air hit them like a physical blow, carrying a dense wall of fine grey stone dust that turned the gallery from a lit working space to a solid grey nothing in under two seconds.
The cage arrived seven seconds later.
Thomas pulled Caleb in by the collar.
The cage began to rise.
Below them, as the elevator platform cleared the third-level gallery entrance, the last visual information either man received was the sight of the western corridor: solid oak timbers gone, the ceiling line collapsed into a continuous boulder pile that ran from the far wall to a point roughly six metres short of where they were standing.
Beyond that point, the gallery was sealed.
Caleb pressed both fists against the elevator cage mesh and stared down at the disappearing gallery level.
Thomas put a hand on his shoulder.
"He went to the rear alcove," Thomas said.
"I heard him respond and move before the sound wave hit."
"The rear alcove has a solid granite ceiling with no limestone cap overlay."
"He is not under the collapsed section."
Caleb said nothing.
He was running a different set of calculations: oxygen volume of the rear alcove, groundwater inflow rate under saturated soil conditions, temperature, time.
He was not reassured by his own arithmetic.
But Thomas was right about one thing.
Toby had moved fast, and he had moved to exactly the right place.
That was worth something.
That was worth a great deal.