The mystery of Gruppe Eisbar's end became clear in my mind now. The wolf-pack had dived into the Glory Hole at a time when the gas was still building up. Therefore the air inside the Glory Hole was pure when the captains rowed themselves ashore to the graveyard in their rubber dinghies. Shelborne must have known there was a methane fissure under the graveyard toolshed and with brilliant opportunism had induced the captains to stay there and close the door. Then pressure had built up, the gas flooding into the Glory Hole beneath and the toolshed above, destroying Gruppe Eisbar and the captains. 'The 'fauler Zauber' must have been, as I had surmised, the incoherencies of the dying radio operator.
The key, I realized, was the intermittent nature of the Bells — the balance between gas and flood build-up. Shelborne had learned the secret and knew when to get out — for example, the night we had seen him from the Malgas fleeing to Sudhuk. The Glory Hole faced into the prevailing wind and Mercury was relatively safe while the south-western ventilated it; the island could become fatal when it was calm. My dive and discovery of the oxygenless sea and harmless gas had merely bedevilled the whole thing.
What a fool I had been over the Mazy Zed's last mining operation, confusing the real killer and the innocent sea-bed gas! It was at my suggestion that the pumps had been laid right into the death-mouth of the Glory Hole, and they had filled the 'tween-decks with the swift, near-odourless killer before the men knew what was happening. I remembered how I had heard the Bells strongly before we went ashore. Out in the open, the deck hands had escaped, as indeed we had on the island where the wind blew the gas away. Shelborne had made his threat to annihilate the crew in the knowledge that the Mazy Zed's powerful pumps would suck up the methane. And Bob Sheriff had died by running into a big pocket as he went past the open-grained quicksands in his boat.
I felt myself being lifted into the vent. If the methane pocket under me beat me to it… I'd rise out of the cavern all right — I'd rise as a dead man. The quicker I got out, the more chance Koeltas would have. My fingers clutched frantically at the water-worn rock. I found a hold, fought, slipped, swung myself clear of the water. It didn't seem more than about a dozen feet to the surface, and it was three across. Higher, it was too smooth for holds. I had the only one. Koeltas splashed in terror. The rifle! I reached past his fear-struck face and wrenched it free, jamming its butt to one wall, barrel to the other. He snatched the sling and hung on, half-in, half-out the water. There as only one way of getting up. I threw my body backward, smashing with a bone-jarring jolt, into the back wall. Feet clamped against the opposite wall, I levered and jerked myself upwards in a skin-ripping series of convulsions. Koeltas followed. I reached ground level and shot out backwards, like a fish out of a seine net, on to the soft sand. Within seconds, Koeltas was there, still clutching his rifle. I jumped to my feet, half-blind in the searing sun, and ran from the death at our heels. Fifty, one hundred yards. Then I was up to my waist.
The blowhole was on the fringe of the quicksands.
My eyes, adapted bat-like to the darkness of the cavern, began to focus properly in the bright light.
I shouted to Koeltas blundering towards me. 'The rifle — pull me out with the strap!'
We had emerged on the high north-eastern shoulder of the Long Wall, next to the quicksands. If the Bells started in earnest, it would be fatal to stay — the pocket from which we had fled was small and must have dissipated itself harmlessly in the open. The soft sand trembled under me. The quicksands, the river-bed and the shoreline would soon be a death-trap. Our only route was down the Long Wall.
I grabbed the gunstrap and Koeltas eased me out of the sand's lethal hold.
The Long Wall! A narrow ledge, about three feet wide, followed the loose contour of the cliff. Koeltas and I edged towards it, fearful to start a landslide which would hurl us on to the rocks hundreds of feet below. A helio of light came from the far side of the quicksands, it was Shelborne! There was no mistaking the tall figure. He seemed to have a large pack on his back. It wasn't the pack I was interested in, however — in his hand was a heavy revolver which was not the Borchardt. Well, if he wanted to shoot it out, he'd get more than he bargained for.
'Give me the gun!' I ordered Koeltas.
'No — I shoot the bastard.'
My anger ignited against the hurrying figure. How many dead lay at his door! The methane had beaten him, so he had chosen to sit on the fountainhead, the richest poor man in the world, unable to do a thing about it himself and passionately refusing to let anyone else.
'Give me the gun!'
I took the weapon and worked the bolt to see it was running free. With infinite care, our bodies and faces clamped against the sand incline, we inched down towards the path. We had reached within feet of it when a bullet dug into the sand within a foot of my arm. The report was simultaneous. I glanced up: Shelborne lay peering at us, fiddling with the revolver for the next shot — perhaps it was jammed with sand. I could not unstrap the Remington to fire. It was a poor shot to miss me at that range. He seemed to be doing something to the barrel. Already he had had time to pick me off with a couple of snapshots before I reached the path and the safety of its overhang.
I let go and slid blindly. My tattered veldskoens bit on the harder path. For a moment I thought the weight of the rifle would overbalance me to certain death far below. I teetered, regained balance, and slipped to safety, unslinging the rifle to cover Koeltas. The Tartar-faced. skipper was right behind me, however. We ran crouched along the ledge until we had put the shoulder of the Long Wall between ourselves and Shelborne. We paused, gasping. The whole pathway seemed to sway nauseatingly.
'Jesus!' exclaimed Koeltas. 'Even here, the bladdy country shakes!'
The Long Wall gave vertiginously. It may not have been more than an inch or two, but it seemed like a malign force trying to shake us off. Talk softly! A loud sound would bring down the blancmange-like cliff on top of us.
'Come!' I whispered.
We eased along the ledge until it began to curve sharply inwards.
Koeltas held up a hand. 'He follows!'
Shelborne knew the Long Wall and it would be easy for him, once we had turned the shoulder facing Sudhuk, to pick us off on the one-thousand-foot incline to the beach. I wasn't going to give him the chance. Ahead was a buttress: I'd wait for Shelborne there — with the Remington.
We slipped round the corner: here the ledge widened into a shallow embankment about ten feet wide and fifty long. I lay down and set my sights at maximum depression. I worked the bolt and reloaded. There would be no mistake. I cuddled the butt against my shoulder.
Shelborne's speed caught me. I had expected a stealthy approach with a snapshot, but he whipped round the corner at a half-run, crouching low. He swung in under my sights. Before I could drop them I felt the heavy slug burn into my shoulder, close against the neck. As I half-rose in agony, I could not help admiring his superb shooting. His momentum had carried him round the corner, but he was already starting to back away to safety as I lifted the gun. The needle of the foresight rested in the middle of his chest, hard and clear against the black sealskin.
Koeltas was at my side. 'Skiet — shoot!' he sobbed. 'You've got the bastard — skiet!'
My eyes blurred and my finger would not come hard against the trigger. Take it easy, I told myself, you've got time and he's a perfect target. My left shoulder and neck were red-hot agony. I blinked my eyes to clear them. The elbow of my left arm, steadying the gun, felt weak. The muscle slackened. My mind was stunned, yawing with the pain. I could feel the blood running down inside my shirt. Why in God's name doesn't he shoot again? The thought drummed through my mind. He knows, blast him, he knows it was a killing shot and he won't have to waste another; I won't have the strength before I die to pull the trigger. He stood, the heavy black pistol hanging loosely by his side, smiling, upright, unafraid.