What have I to do with you? he has a desire to say to somebody at random.

Then he can go.

The few paces across the open, dazzlingly light space, with the roof of perpetual night above it, over to the glass compartment. His companion is standing inside it, lonely and miserable after his watch, his eyes clamped fast to the warning lamp as his own always are. The lamp has just come on. His companion stands playing on the switches, just as practised as himself. The van slithers into sight and is let in.

He enters by the glass door, about to nod: You can go now, I’m here. Instantly he turns numb: the man in front of him has turned away from the lamp and towards him, and he is a stranger, not the man who ought to be here, not the one who relieved him a few hours ago. For a second the stranger stares at him savagely, then turns back to the dead lamp again.

The sentry’s knees have turned to water. What has happened? Where is the right man? Who is this? Those savage eyes that met his! The right man has been removed by force; the sentry knows it at once. That sort of thing is usual in the house now. He’s going to knock me down too. Someone will do it before I – Shout! Run! – but he is rigid with terror and cannot move his feet. The other is wearing the right clothes, the clothes that belong to the missing man. And the shrilling alarm has not gone off. This man must have had several others with him and has somehow found out the secret code that opens the steel door. They managed to do it while he was asleep and dreaming bad dreams.

What has happened affects him twice as strongly because it is at this spot. He has looked into eyes clouded with tension and hate, dark with savagery.

They have found me, he thinks inconsequentially. They have found me, as I knew they would.

And suddenly he knows: I was certain this was going to happen. You wretch! he says to himself, his teeth chattering as he stands rooted to the spot, thousands have passed this place! You have let thousands of lost souls in here – now you’ll be paid back. You have known it all along.

The blood returns to his limbs. He can move them. And his eyes, that were distorted with fear, can focus again. He will run. He dares not attempt to attack the man and knock him down. He suspects that he would find himself lying crushed in an instant. But run –

‘Halt!’ says the stranger, like a gunshot.

Yes, he will halt. Nailed down again: a hand comes out of the cloak and a weapon is pointing at him, or is it only a finger? He does not know, he must simply halt – through the power exerted on him by this stranger.