“Come here, Togo,” he commanded.

The Jap obeyed with alacrity.

“I want you to show these men how to open that door. Understand?”

The little yellow man instantly donned a servile manner, as though he realized that the overlordship of Brown was over, and new masters must now be served.

Leading the way to the tank, he descended into the huge hollow, closely followed by O’Hara and two of the other men.

After they had made their way to the farther end of the tank, the Jap suddenly stooped and touched something that seemed to be one of the rivets that held the giant steel tank together. Instantly the steel walls moved as O’Hara had seen them do earlier, and the aperture leading to the cave opened up directly in front of them. The men marvelled at the ingenuity which had devised this hidden retreat.

O’Hara was the first to file through the opening and descend into the depths of the cave.

“You next!” said one of the detectives to the Jap, as the latter was edging to one side.

The oriental obeyed without a word, followed by the two detectives.

It was several minutes before the men were able to make out their surroundings in the dim light of the gloomy interior.