“Help me to secure the gate,” said Leonard presently.

In another minute the great iron bar had been dropped into its place, and Leonard withdrew the key and put it in his pocket.

“Why do you secure the door, Baas?” whispered Otter.

“To keep the real Pierre out, in case he should come this way. Two Pierres would be one too many at this game. Now we must win or perish.”

Then they crept along the embankment till they gained the shelter of the hut or barrack-shed which stood with its back to the dike that separated the Nest from the slave camp. Happily none saw them, and there were no dogs in the place. Dogs make a noise at inconvenient times, therefore slave-dealers do not love them.

The end of the shed behind which they were crouching was situated some eight or ten paces from the drawbridge, that formed the only path of entry to the slave camp.

“Baas,” said Otter, “let me go forward and look. My eyes are the eyes of a cat; I can see in the dark. Perhaps the bridge is down.”

Without waiting for an answer, he crept forward on his hands and knees so quietly that they could scarcely hear a movement. Notwithstanding his white dress, there was little chance of his being seen, for the shadow of the shed was dense and a fringe of rushes grew along the edge of the dike.

Five minutes passed — ten minutes passed, and Otter did not return. Leonard’s anxiety grew very keen.

“Let us go and see what happened, mother,” he whispered to Soa.

They crept along to the end of the shed. Within a yard of it they discovered the arms and clothes of Otter. But Otter! Where was he?

“The Black One has deserted us,” said Soa beneath her breath.

“Never!” answered Leonard.

By now the clouds were breaking before the wind, which was rising steadily, and some stars shone out, giving a little light. The dike lay deep between its banks and was not more than twenty feet in width, so that the air did not ruffle it; moreover, as any observer of nature will have noticed, the surface of still water is never quite dark, even on much blacker nights than this.

Why had Otter taken off his clothes, Leonard wondered? Evidently that he might go into the water. And what could he want to go into the water for, unless it was that his heart failed him and, as Soa suggested, he had deserted. But this was impossible, for he knew well that the dwarf would die first. In his great perplexity Leonard stared at the dike. Now he could see that on its further side rose a flight of wooden steps, protected at the top by gates and that a man was seated on the lowest step, with a rifle beside him, his feet hanging down to within a few inches of the surface of the dike. It must be the sentry.

Next instant Leonard saw something else. Beneath the feet of the man a ripple grew on the face of the deep water, and something gleamed in the ripple like to the flash of steel. Then a small black object projected itself towards the feet of the sentry, who was half asleep and humming to himself drowsily. Suddenly he saw the man slide from his seat as though by magic. He said nothing, but making one ineffectual grasp at some rushes, he vanished into the deeps below. For a minute or more Leonard could distinguish a slight disturbance on the surface of the water, and that was all.

Now he guessed what had happened. Otter had dived, and rising beneath the feet of the man, he seized him, and with a sudden movement dragged him down to death by drowning. Either this, or an alligator had taken him, and that flash was the flash of his fangs.

As Leonard thought thus a dark form rose gasping at the foot of the steps; it drew itself out of the water and slipped stealthily up them. It was Otter, and he held a knife in his hand. Now the dwarf vanished through the gates into the little guard-house at the top of the embankment. Another minute, and ropes began to creak. Then the tall drawbridge, standing upright like a scaffold against the sky, was seen to bend itself forward. Down it came very softly, and the slave-camp was open to them. Again the black shape appeared, this time on the bridge.

“Come along,” whispered Leonard to his companion; “that hero Otter has drowned the sentry and won the bridge. Stop, pick up his clothes and arms.”

At that moment Otter himself arrived. “Quick,” he said, “come over, Baas, before they see that the bridge is down. Give me my clothes and the gun.”

“All right, here they are,” answered Leonard, and in another minute they were over the bridge and standing on the parapet of the slave-camp.

“Into the guard-house, Baas; the windlass is there, but no man.”

They entered: a lamp was burning in the place. Otter seized the handle of the windlass and began to wind. He was naked, and it was a wonderful sight to see the muscles starting out in knots on his huge but dwarfish frame as he strained at the weight of the bridge.

Presently it was up, and, leaning on the handle of the wheel, Otter chuckled aloud.

“Now we are safe for a time,” he said, “and I will dress myself. Let the Baas forgive me for appearing thus before him — I, who am so ugly.”

“Tell us the tale, Otter.”

“It is short, Baas,” the dwarf replied, as he put on his robe and turban. “When I left you I watched, I who can see in the dark, and in a little while I saw the guard come down the steps and sit by the edge of the water. He was sleepy, for he yawned and lit a roll of paper to smoke it. Presently it went out, and he had no more matches. He looked up to the house there, but was too lazy to fetch them; then I guessed that he was alone, for else he would have called to his companion for fire. Now he grew sleepier, and I said to myself, ‘Otter, Otter, how can you kill this man silently? You must not shoot, because of the noise; and if you throw a knife or a spear, you may miss, or wound him only.’ And my snake spoke in my heart and answered, ‘Otter, Otter, dive, seize his feet, and drag him down swiftly and stamp him into the mud, you who are half a fish and can swim as no other man can swim. Do it at once, Otter, before the light comes and men can see the drawbridge move.’

“Well, and so I did it, Baas. Wow! I trod him deep into the mire, I trampled him as an ox tramples corn upon a threshing-floor. Never will he come up again. After that I rose and ran into the guard-house, fearing lest there might be another whom I must silence also, for when I was a slave two always kept watch. But the place was empty, so I let the bridge down. Ah! I remembered how it worked. And that is the tale, Baas.”

“A great tale, Otter, but it is not finished yet. Now let us to the slaves. Come, take the light and lead the way. Here we are safe, is it not so?”

“Here, Baas, we are safe, for none can reach us except by storm, and yonder is the big gun which turns upon itself. Let us twist the gun round first, so that, if need be, we can fire into the camp.”

“I don’t know much of cannon,” said Leonard doubtfully.

“But I know something, White Man,” said Soa, speaking for the first time. “Mavoom, my master, has a small one up at the Settlement, and often I have helped to fire it for practice and as a signal to boats on the river, and so have many of the men who were carried away, if we can find them yonder.”

“Good,” said Leonard.

A path ran along the top of the embankment to the platform on which the gun was mounted. It was a six-pounder muzzle-loader. Leonard unhooked the rammer and ran it down the muzzle.

“She is loaded,” he said; “now let us swing her round.”

They did so easily enough, bringing the muzzle down upon the Nest camp; then they entered the little hut which stood alongside. Piled up in it, in case of emergency, were half-a-dozen rounds of grape-shot and powder.

“Lots of ammunition, if we should want to use it,” said Leonard. “It never occurred to those gentlemen that a gun can shoot two ways. And now, Otter, lead us to the slaves, quick.”

“This way, Baas, but first we must find the tools; they are in the guard-hut, I suppose.”

So they crept back to the hut, holding their heads as low as possible, for the light was increasing, although the moon was not yet up, and they feared lest they should be seen against the sky-line. Here they found boxes containing nippers, chisels, and other instruments such as are used to undo the irons upon slaves. Also they found the keys of the padlocks that locked the iron bars to which the captives were tethered. Taking a lantern with them, but leaving another burning as before in the hut, lest its absence should excite suspicion, they passed through two strong gates and down the steps on the further side of the embankment. A few paces beyond stood the first slave-shed, a rough erection supported on posts, but without sides.

They entered the shed, Otter leading the way with the lantern. In the middle of it was a path, and on either side of this path ran the long bars to which the captives were fastened in a double row. Perhaps there might have been two hundred and fifty of them in this shed. Here the sights and scenes were such as need not be described. Of the miserable captives some lay on the wet ground, men and women together, trying to forget their sorrows in sleep; but the most part of them were awake, and the sound of moans ran up and down their lines like the moaning of trees in the wind.

When they ............