Cary turned to me. "What made you think it was Trehayne?" he asked. This was better. I looked at Dawson, who was brooding in his chair with his thoughts far away. He was still seeing those eyes fading out under the glare of the electrics between the steel decks of the _Malplaquet_! "It was a sheer guess at first," said I, preserving a decent show of modesty. "When I heard how the enemy plotted and Dawson counter-plotted with all those skilled workmen in his detective service, it occurred to me that an enemy with imagination might counter-counterplot by getting men inside Dawson's defences. I couldn't see how one would work it, but if German agents, say, could manage to become trusted servants of Dawson himself, they would have the time of their lives. So far I was guessing at a possibility, however improbable it might seem. Then when Dawson told us that he had sent Trehayne into the _Antigone_ and that he was the one factor common to both vessels--the workmen and the maintenance part were all different--I began to feel that my wild theory might have something in it. I didn't say anything to you, Cary, or to Dawson--he despises theories. Afterwards Trehayne came in and I spoke to him, and he to me, in French. He did not utter a dozen words altogether, but I was absolutely certain that his French had not been learned at an English public school and during short trips on the Continent. I know too much of English school French and of one's opportunities to learn upon Continental trips. It took me three years of hard work to recover from the sort of French which I learned at school, and I am not well yet. The French spoken by Trehayne was the French of the nursery. It was almost, if not quite, his mother tongue, just as his English was. Trehayne's French accent did not fit into Trehayne's history as retailed to us by Dawson. From that moment I plumped for Trehayne as the cutter of gun wires." Dawson had been listening, though he showed no interest in my speech. When I had quite finished, and was basking in the respectful admiration emanating from dear old Cary, he upset over me a bucket of very cold water. "Very pretty," said he. "But answer one question. Why did I send Trehayne to the _Antigone_?" "Why? How can I tell? You said it was to make sure that the shore party were all off the ship."