‘There are shells there all right, sir, but those devils are guarding them … They were looking at me as I cut them loose …’ His straggly hair bristled in horror. ‘Not at this spot, sahib!’

The captain opened the shells; two were empty but the third contained a pearl the size of a pea, as round as a drop of mercury. Captain van Toch studied in turn the pearl and the Singhalese who was crouching in a heap on the ground.

‘You, boy,’ he said hesitantly, ‘you wouldn’t like to go down there once more?’

The Singhalese shook his head speechlessly.

Captain van Toch felt a strong itch on his tongue to blaspheme. But to his surprise he found that he was talking quietly and almost gently: ‘Don’t be afraid, boy. And what do those … devils … look like?’

‘Like little children,’ the Singhalese breathed. ‘They’ve got a tail and they are this tall,’ and he indicated about four feet from the ground. ‘They stood all around me and watched what I was doing there … there was a whole ring of them around me …’ The Singhalese began to tremble. ‘Sahib! Not here, sahib!’

Captain van Toch reflected. ‘And tell me, do they blink their lower lids, or what?’

‘I don’t know, sir,’ the Singhalese croaked. ‘There’s … ten thousands of them there!’

The captain looked round for the other Singhalese. He was standing some 150 yards off, casually waiting with his arms folded over his shoulders. It is true, of course, that when a chap is naked he’s got nowhere to put his hands except on his own shoulders. The captain made a silent signal to him and the short Singhalese jumped into the water. Three minutes and fifty seconds later he emerged again and with slippery hands slithered up the rocks.

‘Well, get out then,’ the captain shouted. But then he looked more closely and already he was leaping over the boulders towards those desperately groping hands; you’d never credit such a bulk with such agility. He just managed to snatch hold in time of one hand, and panting he dragged the Singhalese out of the water. Then he laid him down on a rock and mopped his sweat. The Singhalese was lying motionless: one of his shins was skinned to the bone, evidently by a rock, but otherwise he was in one piece. The captain lifted his eyelid: only the white of his upturned eyes was visible. He had no shells and no knife.

At just that moment the boat with the crew closed in towards the shore. ‘Sir,’ the Swede Jensen shouted, ‘there are sharks here. Will you carry on fishing?’

‘No,’ said the captain. ‘Pull in here and pick up these two.’

‘Look, sir,’ Jensen pointed out as they were returning to the ship; ‘look how suddenly it gets shallow here. All the way from here to the shore,’ he pointed out, poking his oar in the water. ‘Just as if there was some kind of dam here under the water.’ Not till he was on the boat did the short Singhalese come round. He sat with his knees drawn up to his chin and was shaking all over. The captain sent the men away and sat down with his legs straddled.

‘Well, let’s have it,’ he said. ‘What did you see there?’

‘Djins, sahib,’ the short Singhalese whispered. Now even his eyelids were beginning to tremble and little pimples of gooseflesh erupted all over his body.

Captain van Toch cleared his throat. ‘And … what do they look like?’

‘Like … like …’ A strip of white again began to appear in the Singhalese’s eyes.