Yvonne's up and running before my aching body can even get to its feet. She sprints to the rear of the roof and hops into the seat of her skybike. The headlamps come on as she revs the engine.

"Hurry up, old man!" she yells.

"Smart-mouthed little..." She's putting on her helmet as I climb into the rear seat. The thing's a souped-up old pre-war model that would make a collector drool. I'm hardly even settled in when she kicks the antigrav boosters and we rocket off the roof into ...