She grabbed Caleb under the arms and stood him up. “Come on, you two, we have to get out of this corridor.” Chivvying them along, she marched toward the exit at the end of the connecting tube. The airlock at the end led to the roundabout, which was the central hub of the station. All tunnels and corridors, for five levels, led from the roundabout to every part of the structure.

As she approached the pressure door, the building began to shake again. At first barely perceptible, the shaking seemed to get stronger moment by moment. Emilia broke into a run, dragging her boys by the hands. Caleb, unable to keep up, began to cry. She held him in the air, easily straight-arming him in the one-third gravity, as she sprinted for the hatch.

As Emilia rushed through the airlock, there was a crunch and a bang behind her. A sudden wind blew in her face, just as a klaxon started sounding. She stopped and turned, to see the pressure door slam shut from the ceiling. She looked through the porthole on the door. The corridor had buckled halfway along, and one of the view windows had popped out of its frame. A half-dozen people, trapped in the corridor, were being dragged by the escaping air toward the gap.

One woman looked directly at Emilia, terror plain on her face.

I know her. She passed that woman most days, going in the opposite direction. They would nod and smile, and occasionally exchange greetings. As Emilia watched, the woman was sucked out through the window, still scrabbling at the floor and walls.

“What’s happening, Mom? Can I see?” Ian held his hands up, requesting a lift. Beside him, Caleb jumped up and down in a vain attempt to get enough height to see through the porthole.

Still in shock, Emilia turned and looked around the roundabout. Dozens of stunned faces looked back at her or at each other.

The klaxon cut off and a voice announced over the P.A., “All personnel to evacuation stations. This is not a drill. All personnel to evacuation stations.”

Emilia’s eyes widened, and she looked around frantically for any indication of the location of the nearest evacuation station. A red flashing light caught her eye. She turned toward it just as another tremor hit. There was no buildup. One moment the floor was steady; the next, she was being bounced around like popcorn. People screamed; some screams cut off abruptly.

As soon as the tremors abated, Emilia grabbed her children and sprinted for the flashing light. This time, she put even less care into making sure the boys were feet-down–head-up. She realized, mid-sprint, that she had Caleb by the back of his pants, and was carrying him like a briefcase. Both boys howled in terror, more from picking up their mother’s fear than from any understanding of the situation.