Then the gunfire started.

It was not the random shooting of street thugs.

These were synchronized, suppressed bursts that chipped the plaster off the ceiling.

Marcus had pushed me toward the iron door of the cellar stairs.

“I have the gate, Adrian!” he had roared over the noise of the alarms.

“Go! Lock it behind you!”

I had looked back once to see him kneeling by the heavy iron grate, his rifle spitting fire into the smoke.

Then the iron gate had slammed down, its heavy lock clicking into place.

That was the last time I saw him before Caleb’s face appeared on my screen.

Now, inside the concrete vault, the silence was heavy.

The air smelled of old dust and cold copper.

“Daniel, check the seal on the ventilation shafts,” I said, putting my phone in my pocket.

Daniel nodded and walked to the digital control board near the door.

His fingers tapped the keys, his face illuminated by the green light of the screen.

“The main intake is clear, but the exhaust is showing a pressure drop,” Daniel said.

“They are already blocking it.”