His own reaction was a hangover from the past, when he had gotten from their fathers a never-diminished gusto and optimism. They had never faltered. Or they had seemed not to falter. Perhaps they were more self-controlled and would have been ashamed to let him see their dismay. Their sons were more open, less vulnerable to shame. Moreover, if he, who prided him-self on his logical behaviour, was not doubtful about pushing on, then he must be missing something in his own character.

Doc Caliban thought, Well, not really. It's just that I know that I have more capabilities than they do.

Now was no time for soul-searching. He could do that when he retired to that hidden stronghold which had once been in the far north but which he had relocated at the bottom of a lake. Lately, when he had retreated, he had ceased to work on scientific devices and had taken to pursuing Oriental philosophies and their techniques.

He shook his head. Pauncho said, 'What's the matter, Doc?'

Doc put his hands on their wrists and squeezed a message. Then he said, loudly, 'We'll go ahead, take what comes, play it by ear!'

He turned and Pauncho got on one side and Barney on the other as they started across the room, which was about twenty feet high, sixty long, and forty wide.

Doc took two steps, whirled, and flashed back into the tunnel, sped crouching down it, and dived for the nearest rifle between the wall and the stone. Having seized it, he turned over and slid under it, releasing it only when Barney grabbed it. The two had started immediately after him but they were a few seconds behind since he was so swift. To any watcher he must have seemed almost a blur.

Pauncho, who was three times as strong as Barney but not as quick on his feet, caught up with Barney and grabbed his rifle. In a short time, they each had hold of a gun.

They waited for a moment. That the block had not withdrawn and then slammed in when Doc made his dive seemed to indicate that it was not being remote controlled. A watcher should have been startled by Doc's sudden return and operated the controls in sheer reflex.

It was also possible that the renewed hostility of the birds had come from an automatic mechanism. Doc had triggered off an alarm, perhaps by cutting across a beam.

While Pauncho braced himself between two rifles, and Barney gripped one, Doc slid out and then duck-ran back to the room. He returned with three more rifles. The two took them while Doc gripped the two rifles jammed against the wall and then he dived out and away, just in case there was a remote controller. The stone block did not move.

This room was without furniture or decoration except for a black, red-headed eagle, twice as large as a man, painted on a wall, and a ceramic container which might have been used for bathing small humans. The archway led to another round tunnel, but this was large enough for even Doc Caliban to stand erect in. At irregular intervals along the tunnel, about three feet up, were painted the symbols - squares with looped corners - which the Finns called hannunkaavuna and the Swedes St. Hans's arms. Doc knew this symbol well. It was carved on the staff which the Speaker for the Nine carried during the annual ceremonies in the caves in the mountains in Central Africa. The upper half of the staff bore a carved ankh, the cross with a circle on top, a symbol as ancient as Egypt.

The hannunkaavuna made him think briefly of Grandrith. That tall man with the black hair, grey eyes, handsome near-aquiline face, and Apollo-like body with its Herculean strength-his half-brother - should be near the coast of Gabon now. He would land there and proceed on foot across Central Africa, sticking largely to the belt of the rain forest, where few humans would see him. And then he would come up onto the bank of the mountains which held the caves of the Nine, and he would do what he could there. If he was confined to scouting and spying, he would wait until his brother could join him in an attack on the Nine during the annual ceremonies. If he had a chance to kill one of the Nine, he would do so.

The memory of pain twinged him in the back of the neck and elsewhere. His fight with Grandrith had not been without loss and agony.

They got out of the tunnel without incident. Pauncho wiped sweat off his shelving brow and said, 'Whoo!’

Barney said, 'I kept expecting the side of the wall to jump out at us.'

Doc looked around. This room had hexagonal corners and was painted with many scenes of long-bearded squat little men fighting crocodile-sized creatures looking exactly like the stuffed Tatzelwurm. The focus of the battle was a big pile of gold rocks. A twilight illumination came from naked plastic bulbs set in widely separated brackets on the walls. Wires ran from them to black boxes on the floor.

Pauncho said, 'Listen, Doc, do you think that once there may have been big whatchamaycallems, and these gave rise to the legends of the dragons?'

'Your guess is as good as mine,' Caliban said, and he led them to the next archway. This was painted black, and the tunnel was black. They proceeded ten yards when they came to a hole in the centre of the floor. Doc pointed his headlight down it, making sure that his rifle was still held at the proper angle across his belly. The shaft went straight down for about twenty feet and then became a hole in the ceiling of another tunnel. A section of wooden ladder lying flat on the floor was visible.

The atomiser revealed that someone had gone down the shaft by putting their back to one wall and their feet against the other. It also indicated footprints going on in this tunnel, but the light from the prints was not as bright as that on the walls of the shaft.

'It could be another trap,' Doc squeezed on Barney's arm. Barney transmitted the same message to Pauncho.

'We're playing follow-the-leader,' Barney squeezed back. His thin foxily handsome face looked eager. Pauncho was grinning like an orangutan dreaming of durian fruit.

Iwaldi seemed to be going to the lower levels. At least, that would be the natural direction for him to go when his home was invaded. Perhaps he did not know that his traps had killed all of one party of invaders and that just three men were tracking him. Perhaps he did, and he was crouching in some room and watching them even now, waiting for the proper moment so he could press a button or pull a lever or just watch while an automatic trap was sprung.

Doc leaned over and dropped his rifle, butt first. It struck and toppled over. He waited. Nothing happened. There was nothing to do but go down the shaft then. Near its bottom he removed a suction disc from his pocket, stuck it against the shaft wall, and lowered him-self by his left hand down from the shaft, his legs drawn up. He swung like a gibbon from a branch, turning to take in the round tunnel which ran for ten yards in either direction and then curved out of sight. The ceiling was eleven feet from the floor, and the greatest distance between the walls was twelve. There were eight bulbs on brackets along the walls.

'How is it, Doc?' whispered Pauncho.

Caliban looked up. The ugly but congenial face hung over him.

'Only one way to find out,' he said. He released his grip on the handle of the disc, it fell, he grabbed it, and he dropped down to the floor. But his other hand had his gasgun out before his feet struck the stone.

Pauncho came down, grunting, and then Barney.

The moment Barney landed, the world seemed to tilt. Doc made a leap forward for the shaft with his left hand, which still held the disc, extended. And when the disc slapped onto the inner edge of the lip of the shaft, he squeezed down on the handle. The disc held, and he hung there, while the ladder, his rifle, and his two friends went down the slope of the tunnel, which had suddenly dropped and was rapidly becoming vertical.