"We're certainly not that, anyhow," Dennis agreed emphatically. "It is a real mystery, Ronald, my boy. A real danger, as well, I'm afraid. But we'll stick at it till the end." "Thanks, old fellow," I said simply, and then I added, "I wonder what can have become of Hilderman?" "Gad!" cried Dennis, in sudden alarm. "He can't have fallen into the river by any chance?" We jumped to our feet and looked about us. "No," I said presently, "he hasn't fallen into the river." And I pointed a finger out to sea. The _Baltimore II._, churning a frantic way across to Glasnabinnie, seemed to divide the intervening water in one great white slash. "I wonder," said Dennis quietly, "_is_ that funk, or isn't it?" We watched the diminishing craft for a minute or two in silence, and finally decided to keep an open mind on the subject until we might have an opportunity to see Hilderman and hear his own explanation. "Talking about explanations, what about the left-handed schoolmaster with the red-headed wife, or whatever it was?" I asked. "That was a bit of luck," said Dennis modestly, "and I will admit, if you like, that we owe that to Garnesk." "Garnesk wasn't there," I protested. "No," my friend admitted, "he wasn't there at the time, but he put me on the look-out for a left-handed sailor. I was very much impressed with his deductions about the man who stole Miss McLeod's dog, and I determined to be on the look-out for a left-handed man. I also admit that I carefully watched everyone we met, especially the fishermen at Mallaig, to see if I could detect the sort of man I wanted. I was rewarded when we were pulled out to the _Fiona_ by those two men of Fuller's. One of them was red-headed, you remember? Well, that man was left-handed. It was very easy to observe that by the way he held his oar and generally handled things. Of course I was very bucked about it, so I paid very close attention to him. He wore a wedding-ring--ergo, he was married. It is not conclusive, of course, but a fairly safe guess when you're playing at toy detectives. So when I found the knife I looked for some sign that it belonged to him, and found it. It was all quite simple." "I daresay it will be when you explain it, but you haven't in the least explained it yet," I pointed out. "How about the schoolmaster and all that, and what made you think the knife belonged to him." "Simply because he was very probably--working on the law of averages--the only left-handed man among the crew, and that knife belonged to a left-handed man." "But my dear old fellow," I cried, "you don't seriously mean to tell me that you can say whether a man is left-handed or not by looking at marks on the handle of his knife?" "Not on the handle," Dennis explained; "on the blade. Have you got a knife on you?" I produced my pen-knife. "I'll trust you with it," I declared confidently. "I've never held any secrets from you, Den."