<p> &ldquo;And then I learned that, by excavating in one of the cellars of the house, he and some companions had made their way into the vaults under the great public building I have mentioned before. The blowing up of a whole wing was a certainty as soon as the materials were ready. </p> <p> &ldquo;I was not so appalled at the stupidity of that move as I might have been had not the usefulness of our centre in Hermione Street become already very problematical. In fact, in my opinion it was much more of a police trap by this time than anything else. </p> <p> &ldquo;What was necessary now was to discover what, or rather who, was wrong, and I managed at last to get that idea into Horne&rsquo;s head. He glared, perplexed, his nostrils working as if he were sniffing treachery in the air. </p> <p> &ldquo;And here comes a piece of work which will no doubt strike you as a sort of theatrical expedient. And yet what else could have been done? The problem was to find out the untrustworthy member of the group. But no suspicion could be fastened on one more than another. To set a watch upon them all was not very practicable. Besides, that proceeding often fails. In any case, it takes time, and the danger was pressing. I felt certain that the premises in Hermione Street would be ultimately raided, though the police had evidently such confidence in the informer that the house, for the time being, was not even watched. Horne was positive on that point. Under the circumstances it was an unfavourable symptom. Something had to be done quickly. </p> <p> &ldquo;I decided to organize a raid myself upon the group. Do you understand? A raid of other trusty comrades personating the police. A conspiracy within a conspiracy. You see the object of it, of course. When apparently about to be arrested I hoped the informer would betray himself in some way or other; either by some unguarded act or simply by his unconcerned demeanour, for instance. Of coarse there was the risk of complete failure and the no lesser risk of some fatal accident in the course of resistance, perhaps, or in the efforts at escape. For, as you will easily see, the Hermione Street group had to be actually and completely taken unawares, as I was sure they would be by the real police before very long. The informer was amongst them, and Horne alone could be let into the secret of my plan. </p> <p> &ldquo;I will not enter into the detail of my preparations. It was not very easy to arrange, but it was done very well, with a really convincing effect. The sham police invaded the restaurant, whose shutters were immediately put up. The surprise was perfect. Most of the Hermione Street party were