‘What are you doing now?’ said Goldwasser.

‘We’re starting a new series to test its behaviour with simpler organisms.’

Samaritan II came back up to the gantry, winched by the crane. There was something about its visible dials and displays that struck Goldwasser.

‘Doesn’t it look a bit sanctimonious to you?’ he asked Macintosh.

‘Aye, it always does after it’s gone over the side. It’s a minor defect. We’ll get it right in development.’

‘But Macintosh, if it enjoys sacrificing itself it’s not taking an ethical decision at all, is it?’

‘I don’t see why it shouldn’t enjoy doing right.’

‘But if it’s enjoyable it’s not self-sacrifice.’

‘By God, Goldwasser, you’re a real puritan! If a thing’s right it’s right, and if you enjoy doing it so much the better.’

‘It may be right. But for God’s sake, Macintosh, it’s not ethically interesting!’

They glared at one another in exasperation. It infuriated Goldwasser to think that this stubborn, slow-witted lump might in certain important ways be more intelligent than he was. He supposed that Macintosh must be no less irritated to think that in the long run his sound, slow-moving brains might not be competitive with Goldwasser’s more flashy mental equipment.

‘Anyway,’ he said, ‘the Queen’s coming down to open your new wing.’

‘I suppose that’s Nunn pulling strings again?’

‘I suppose so.’

‘The Establishment at work once more.’

‘I suppose it means you’ll have to install some experiments in it after all.’

‘It means nothing of the kind.’

‘You’re still going to boycott it?’

‘Certainly. I’ve told you. I’ve told Nunn. I’ll have nothing to do with the new wing. I’ve no use for it. I’m too busy with the Samaritan programme. I’ve told them all along.’

‘There’ll be trouble.’

‘Let there be.’

A large sandbag was winched up to the gantry, and placed side by side with the Samaritan on the raft.

‘Launch her!’ shouted Macintosh.

The raft swung out over the water, and was lowered steadily away. The resonant silence fell once more.

‘There’s a logical flaw here,’ said Goldwasser suddenly, and his voice boomed about the roof.

‘Drop her!’ shouted Macintosh.

The noise of the raft hitting the water joined the reverberations of ‘There’s a logical flaw here’ and ‘Drop her!’ on their complex journeys between wall and wall and tank and ceiling. Samaritan and the sandbag looked at one another impassively as the raft settled. When the deck was awash Samaritan seized the sandbag and attempted to measure the size of its skull. It attempted its four neat movements, frustrated by the un-skull-like shape of the sack, then paused, drew its conclusions, uttered a thoughtful whirr, and became completely still.

‘Good lad,’ said Macintosh under his breath.

The deck of the raft was now completely submerged. Gradually the water rose around Samaritan and the sandbag as they sat stoically accepting their fate. The sandbag was the first to disappear. Then, with a last look of silent martyrdom, Samaritan vanished too. The bulging, shrinking, dark, refracted shape beneath the water went steadily down to the bottom.