"Why, I was at the garden day before yesterday, and a man approached and asked if I was Miss Hargreave. Becoming at once suspicious that something very important was about to happen I signified that I was Miss Hargreave. The man slipped a paper into my hand and hurried off. I took a quick glance at it and was dumfounded to find it utterly blank of writing. At first I thought some joke had been played on me, then I chanced to remember the invisible ink letters you always wrote me. Understanding that you were to visit the cave in the morning, I had one man at the garden take the note. And you never got it!" "Some one shall certainly pay for this carelessness. I'll call up Vroon and Jackson at once. Wait just a moment." He went to the telephone. A low muttering conversation took place. Olga could hear little or none of it. When Braine put the receiver back on the hook his face was not pleasant to see. "That girl!" "What now?" "It seems she had been out horseback riding that morning. She had seen one of the boys cross the field and suddenly disappear; and she was curious to learn what had become of him. With her usual luck she stumbled on the method of opening the door of the cave and went in. She must have been nosing about. She didn't have much time, though, as the boys came up to await me. Evidently she crawled into that old chest and in some inexplicable manner purloined the letter from Jackson's pocket. They left to reconnoiter; and it was then that Jackson discovered his loss. When Florence heard them returning she jumped into the well. And lived through that tunnel! The devil is in it!" "Or out of it, since we consider him our friend." "And I had her in my hands, note and all!" "But with all that water there will not be any writing left on the letter." "Invisible ink is generally indelible and impervious to the action of water; at least the kind I use is. I'd give a thousand for a sight of that letter." [Illustration: FROM THE SHORE CAME ANOTHER DOAT] "And it might be worth a million," Olga suggested. "Not the least doubt of it in my mind. Olga, old girl, it does look as if my star was growing dim. We'll never get our hands on that million. I feel it in my bones. So let's settle down to a campaign of revenge, without any furbelows. I want to twist Hargreave's heart before the game winds up." "You wish really to injure her?" "I do not wish to injure her. Far from it," he replied, smiling evilly. "You want her ... dead?" whispered Olga, paling. "Exactly. I want her dead. And so if all my efforts here come to nothing, so shall Hargreave's. His millions will become waste paper to him. That's revenge. The Persian peach method." "Poison? You shall not! You shall not kill her!" vehemently. "Tender-hearted?" "No. If I must in the end go to prison, so be it; but I refuse to die in the chair."