“As you know, a deal in the stock market practically ruined him,” she went on. “The only way out he could see was the chest that both of us felt was hidden in the lagoon. He never took the monster legend seriously, but always before he had been willing to wait until he could procure some safe appliance to rescue the chest. At that time both of us knew almost exactly where it was. And when the crash came, the sudden need for money and his desperation sent him out in the darkness to procure it. He too was caught in the undersea channel.
“Of course Major Dell was never even menaced by the sink-hole. Likely he had some knowledge of it. He vanished the third night, because first, he realized that Noyes’ testimony would sooner or later convict him of his brother’s murder, and second, because the disappearance of Florey and Nealman had set a good example for him. Some secret business took him into my uncle’s room first, as you guessed. I have no doubt that he was hiding in the dense thickets on the other side of the lagoon all the time—waiting for his chance to procure the treasure and make his escape.
“I don’t know that you’ll believe it, but by this time I had guessed the secret of the lagoon. I didn’t know just how it worked, but I felt there was some kind of an underground outlet that would sweep away any one who tried to wade in the proximity of the treasure. Of course I didn’t suspect Dell—I thought he had merely gone as Uncle Grover had gone, through the sink-hole to his death. When I made my attempt, I went prepared.”
“But how dared you attempt it?” I demanded.
She laughed at my anger. “I wanted to know the truth!” she exclaimed. “I owed it to Uncle Grover—to find out what became of him. I needed the treasure chest, too—for his securities won’t quite balance, he told me, the demands that will be made upon the estate. And finally—maybe there was another reason, too. Perhaps you know what it was.”
The narration could not go on at once. It was one of those moments that a man always remembers, and holds dear when most earthly treasures are as dust. She hadn’t forgotten my own dreams—the plans I had made but which seemed so impossible of fulfillment.
“But how did you dare take the risk?” I demanded.
“There wasn’t any risk—at least, I didn’t think there was. I felt sure that a sink-hole in the bed of the lagoon was the explanation. The plank I dragged out there was plenty big enough to hold me up. You know a floating cake of soap doesn’t go down the sluice as long as the bathtub is any way near full of water. The plank would have held me easily if Dell hadn’t interfered and torn it from my hands.
“Why did he interfere? Of course we can only guess at that. I think he was waiting for a chance to take the treasure himself—and he saw my intention. I suppose he had dreamed about his grandfather’s gold until it was a veritable passion with him—a mania—and he was willing to risk death in the sink-hole sooner than let it go? Likely he meant to tear my hands from the plank but hang on to it himself. Of course it got away from us both. That’s the whole story. Your own wonderful endurance and mastery of swimming saved me. Doesn’t that seem to clear up everything?”
“Almost everything. Yet I don’t see why Dell waited—why he hadn’t got the treasure out some time night before last—or yesterday——”