As soon as they had collected their belongings and stores, they set about to leave the fort, passing through the tunnel in single file, the guide leading the way and Harry Urquhart bringing up the rear.

By the time they entered the forest the afternoon was well advanced, the sun sinking in the heavens. They hoped to reach the British camp that night, but there was no question that darkness would overtake them long before they could do so.

There was little or nothing to fear. The soldiers had driven the Germans from the district. To all intents and purposes the German Cameroons was conquered, and the remnants of the enemy were returning in hot haste towards the Spanish territory to the east.

When Harry Urquhart and his three companions came forth from the entrance to the tunnel they found a heap of hot, charred wood upon the ground. There was no doubt that recently a fire had been burning, and that the picket that guarded the tunnel had retreated only at the eleventh hour.

During the earlier part of the night they traversed the valley, marching in a bee-line towards the bivouac fires of the British camp. They moved forward in the following order--Fernando went first, some distance behind him came Jim Braid and Peter Klein, and a greater distance in the rear was Harry Urquhart.

Harry had been walking for some time with his eyes fixed upon the ground. He was wondering what the end of all this strange business was to be.

He knew that von Hardenberg had stolen the Sunstone, that he carried it upon his person. It was Harry's ambition, the very lodestone of his life, to recover the Sunstone for his uncle. It was von Hardenberg's object to reach the Caves of Zoroaster, and possess himself of the treasure. This was the man's only aim, for which he had proved that he was prepared to sacrifice his country and his honour.

As he walked, Harry was thinking of these things, when, on a sudden, there came a flash of fire, not ten paces to the right. He pulled up with a jerk, and heard a bullet sing past his head like some evil spirit in the darkness. Then there came a stinging sensation in the lobe of an ear, and a moment later he felt the warm blood flowing down his neck.

He saw a figure flying in the night, and with a loud cry took up the pursuit. A few seconds later he had flung himself upon a man who struggled in his grasp. On the instant each seized the other by the throat, and in the moonlight Harry recognized that he had come to death-grips with his cousin, Captain von Hardenberg himself.

No sooner was he aware who his opponent was than he saw at once that here was a chance to capture the Sunstone, and for that end he struggled with the desperation that means more than strength.

Placing one leg behind his adversary, and pressing with all his force upon his chest, he endeavoured to throw von Hardenberg backward. And even as he wrestled he felt the Sunstone, sewn in the lining of the Prussian's coat.

Gradually von Hardenberg was forced backward, and then at last he fell, coming heavily to the ground. In his fall he struck his head against a rock, and after that he lay quite motionless and silent.

Harry could hear the footsteps of approaching men. On one hand Jim Braid and Fernando hastened to the boy's assistance; on the other, the Black Dog came forward with rapidity.

As quick as thought Harry pulled out his pocketknife. He had but to rip open von Hardenberg's coat and the Sunstone was his, their journey was at an end.

A sharp cut with the knife, a hand that trembled with excitement thrust through the opening, and Harry's fingers closed upon the precious relic he had come so many miles to gain.

And, at that moment, a violent blow descended upon his head and stretched him senseless on the ground. The Arab sheikh had come to the assistance of his employer in the nick of time. His quick eyes had taken in the situation at a glance. He had seen the Sunstone in the hands of Harry Urquhart, and, lifting his rifle by the barrel, he had brought down the butt upon the boy's head.

For him to snatch up the Sunstone was the work of an instant. And a moment afterwards the Black Dog was flying in the night, carrying in his arms the unconscious body of von Hardenberg.