The Great White Queen by William le Queux

WE remained fully two hours in the noisome Treasure-chamber of the Sanoms, the early history of which was lost in the mist of legendary lore, then after careful and minute examination of the rifled chests, worked our way to the base of the shaft, and, having ascended, let down the tiny concealed lever, thereby allowing the pressure to increase, and place in position the ingenious contrivance for causing death to the venturesome. Replacing the iron plate that closed the mouth of the well-like aperture, we screwed it down, rendering it water-tight, and, crossing the stones, regained the bank of the lake. Then, having turned back the lever, the flood-gates slowly closed down again, and, ere we mounted our horses to ride back to the city, the waters, fed by the many torrents, had already risen sufficiently to hide the slime-covered entrance to the secret chamber.

One of the greatest thefts in the world's history had been committed, and the question that puzzled us was the identity of the thief. Our first suspicions had fallen upon the Naya, but calmly discussing the question as we rode back, we both became convinced that so critical was the deposed ruler's position, that she would never have undertaken all the risks in removing the treasure. She knew she was in deadly peril of her life, and that every moment lost was of vital importance, therefore it was hardly probable that she would have delayed her departure to secure the wealth of her ancestors.