He shook his head. "We shall see. Here I sit, mon ami. We do not stir out this morning. We await events here." It was at half-past eleven exactly that the summons came. A petit bleu. Poirot tore it open, then handed it to me. It was from Madame Olivier, the world-famous scientist, whom we had visited yesterday in connection with the Halliday case. It asked us to come out to Passy at once. We obeyed the summons without an instant's delay. Madame Olivier received us in the same small salon. I was struck anew with the wonderful power of this woman, with her long nun's face and burning eyes--this brilliant successor of Becquerel and the Curies. She came to the point at once. "Messieurs, you interviewed me yesterday about the disappearance of M. Halliday. I now learn that you returned to the house a second time, and asked to see my secretary, Inez Veroneau. She left the house with you, and has not returned here since." "Is that all, madame?" "No, monsieur, it is not. Last night the laboratory was broken into, and several valuable papers and memoranda were stolen. The thieves had a try for something more precious still, but luckily they failed to open the big safe." "Madame, these are the facts of the case. Your late secretary, Madame Veroneau, was really the Countess Rossakoff, an expert thief, and it was she who was responsible for the disappearance of M. Halliday. How long had she been with you?" "Five months, monsieur. What you say amazes me." "It is true, nevertheless. These papers, were they easy to find? Or do you think an inside knowledge was shown?" "It is rather curious that the thieves knew exactly where to look. You think Inez--" "Yes, I have no doubt that it was upon her information that they acted. But what is this precious thing that the thieves failed to find? Jewels?" Madame Olivier shook her head with a faint smile. "Something much more precious than that, monsieur." She looked round her, then bent forward, lowering her voice. "Radium, monsieur." "Radium?"