She opened the door to the emergency stair, a route favoured by Carry when he was in a hurry to get to work, and began the brief climb to the next floor, unconsciously making her footsteps as light as possible. There was a square landing midway between floors, and Cona had barely reached it when the air was filled with the shrill bleat of an alarm signal.

Shocked, filled with irrational guilt, she clutched her son closer to her and froze against the wall, momentarily unable to decide whether to turn back or goon.

The sound of the alarm caused Mathieu to moan aloud in panic. He backed away from the Department of Supply monitor, knowing that the hail of radiation he had sent blasting through it would have erased programmes and memory alike. For an instant he thought the machine had retained the ability to warn of sabotage, then it dawned on him that there was a still-functioning alarm system somewhere in Sublevel Three, a relic of the days when it had housed a computer centre. This was something he had not even considered, yet another proof that it was foolhardy to plan anything important while under the influence of felicitin…

Why are you standing around? The words reverberated between his temples. Run! RUN!

He dragged open the door of the room and sprinted back the way he had come, moving so fast under adrenalin boost that he could actually hear the rush of air past his ears. His sponge-soled shoes made virtually no sound as he zigzagged through the huge outer room at dangerous speed. The continuing screech of the alarm lent super-human power to his legs as he reached the foot of the emergency stair and hurled himself up it in time-dilated dream-flight, taking four and five steps at each stride, his mouth agape and down-curved, scooping air.

I'm going to be all right, he thought as the floor markers appeared and dropped behind with impossible rapidity, fm going to get away with…