No. IV.- THE RADIUM THIEVES. IT was the day after the sensational release of John Halliday from the hands of the Big Four. The scientist had departed for England, but Poirot and I had remained on in Paris. I was all for energetic proceedings of some kind or other, and Poirot's quiescence annoyed me. “For heaven's sake, Poirot,” I urged, let us be up and at them!” “Admirable, mon ami, admirable! Up where and at whom? Be precise, I beg of you." “At the Big Four, of course." “Cela va sans dire. But how would you set about it?” “The police," I hazarded doubtfully. Poirot smiled. “They would accuse us of romancing. We have nothing to go upon- nothing whatever. We must wait." “Wait for what?” “Wait for them to make a move. See now, in England you all comprehend and adore le boxe. If on

