The four gentlemen turned out of the Rue du Perron down the narrow, ancient and curious Passage de Monnetier, and out of that into a deep arched alley running through a house into another street. Henry, watching from the corner of the Passage de Monnetier, did not dare to follow nearer for some moments. When he had given them a little time, he softly tiptoed to the mouth of the alley. It was one of those deep cobbled passages that run through many houses in the old quarter. It was profoundly dark; Henry could only faintly discern the three figures half-way down it. They seemed to have stopped, and to be bending down as if looking for something on the ground. The spark of an electric torch gleamed suddenly, directed by the little clergyman; its faint disc of light swam over the dirty floor of the passage, till it came to rest on an iron ring that lay flat to the ground. The clergyman seized this ring and jerked at it; after a moment it left the ground in his hand, and with it the flap of a trap-door. Whispers inaudible to Henry passed between the members of the party; then, one by one, the three figures descended through the open trap into the bowels of the earth, and the lid closed upon them. Henry tiptoed forward; should he follow? On the whole--no. On the whole he would wait until Wilbraham, his father-in-law, M. Kratzky, and the clergyman emerged. What, after all, would be the use of finding oneself underground with desperate, detected criminals, whose habit it apparently was to stick at nothing? What, after all, could he do? Henry was shivering, less from fear than excitement. Here, indeed, was a clue. Were they kept immured underground, these unfortunate captive delegates? And did Wilbraham and his criminal associates visit them from time to time with food and drink? Or without? With nothing, perhaps, but taunts? And how many more in Geneva knew of this trap-door and its secret? There were, every one knew, a number of these old _trappons_ in the city, leading usually to disused cellars; their presence excited no suspicion. Probably no one ever used the obscure and hidden trap in this dark alley. It was queer, how sure Henry felt that this curious nocturnal expedition on the part of Charles, his father-in-law, M. Kratzky and the Calvinist pastor had to do with the mystery of the delegates. He knew it beyond a doubt. Nor was he surprised. It came as a consummation of his suspicion and his hopes. Of Charles Wilbraham's villainy he had long been all but sure; of the villainy of M. Kratzky all the world knew; of the villainy of an ammunitions knight and a Calvinist pastor there needed little to convince Henry. But he knew that he must make sure. He must not go to the police, or to the committee, with an unproved tale. He must wait and investigate and prove.