Illumination returned, but at a lower level, emergency lights kicking in. The tower shook again, hard enough to rattle the railings and produce ominous crunches from the joints of the cast-concrete stairs. A low rumble like an approaching subway train came from beneath them. Eddie looked down again. The descending flights no longer receded in perfect alignment; they were now swaying, twisting . . .

But it wasn’t an earthquake.

A new light grew at the bottom of the shaft, a shimmering blue-white glow. Sparks crackled from the metal railings, lightning bolts lancing across the stairwell. The shuddering grew worse – and Macy shrieked as a crack suddenly split the wall beside her. Dust dropped from above . . .

Followed by larger debris.

A brick-sized chunk of concrete smashed on the steps. More pieces tumbled down the shaft. Eddie looked up to find their source—

And saw one of the higher flights of stairs tearing away from the wall.

Other sections cracked as he watched. ‘Jesus! Get off the stairs!’ he shouted. ‘They’re going to collapse!’

He and Macy leapt down to the next landing. He threw the door open and rushed into the access corridor. Cheng and a soldier were right behind them, the others stumbling as the stairs jolted. The first five recovered, piling through the doorway—

The last man was still in the stairwell when the weakened flight higher up broke loose – and fell.

It slammed onto the steps below, sending them plunging in a lethal domino effect. Another flight, then another, extra tons of concrete joining the cascade at each step. By the thirty-ninth floor it was as unstoppable as a runaway locomotive. A deafening bang, and both the landing and the trailing soldier were gone, leaving only swirling dust. More thunderous slams echoed up the stairwell as the flights below were demolished.

Eddie didn’t even have time to be shocked by the soldier’s death. The tower was now rocking, pitching him back and forth. Windows shattered as the entire building strained, battling to stay upright . . .

And failing.

A massive boom of disintegrating concrete from below – and the floor tilted.

Eddie pulled Macy to the side of the corridor. ‘Hold on to me!’ he cried, but there was nothing he could hold himself. He looked down the steepening slope. The offices on this floor were glass-walled, giving a view all the way to the exterior windows. The shorter tower was visible beyond, its mirrored face showing its neighbour. Broken glass ruined the infinite reflections intended by the architects, ragged black holes spattering the image—

The reflection changed.

The perspective of the building in the mirror shifted as the damaged structure tilted towards it. ‘Jesus,’ he gasped. ‘The whole fucking tower’s going to fall over!’ Macy stared at him, shocked – but knowing he wouldn’t have sworn in front of her unless something truly terrible was happening—