"Fine," snaps Rush, in no mood, his voice made thin and strained with the effort required to jam a thin length of rebar beneath one of the more substantial wedges of rubble and lever it out of his way. "Clearly you are not in a citadel any longer."

He turns neatly to face her and jerks his chin in the direction of the thin hairline cracks fanning out across the glass separating them from the seething mass of ocean water beyond.

He does not like the water.

"If you don't mind," he says crisply, "I'm rather interested in not drowning in the near future. Are you."