Next day, in consequence of a note I sent her, we met in one of the sitting-rooms in the further, and at the present moment unoccupied--wing of the hotel. She then told me that her own sitting-room was next to one occupied by a Swedish engineer named Oscar Engstrom, whom I had watched in Lisbon a month before and who was now in Switzerland engaged on some mysterious business which we had not been able to fathom. We strongly suspected, however, from various bits of evidence that had reached us, that the man was in the pay of Germany at the moment, even if he were not one of the regular German agents. When I entered, Madame Gabrielle, smartly attired in a tailor-made gown of navy-blue cloth and a very bewitching hat, was standing at the window, with her pet dog beneath her arm, chatting to the immaculate Luigi, gazing the while on the blue waters of the lake. I found myself reflecting how typically French she was in every detail-- dainty in face and figure, immaculately dressed, and possessing that indefinably vivacious great charm which seems to be the monopoly of the cultured Frenchwoman. She could throw it aside when she chose, such was her wonderful versatility, and assume a mask of dullness and stupidity sufficient to ensure that no one meeting her would give her a second glance. It was a valuable accomplishment, and more than once had carried her safely through a difficult and dangerous situation. To-day, among friends, she was her own sunny self. "Ah, Monsieur Gerald," she cried, springing forward to greet me, "our friend Luigi has been telling me some very strange things--eh?" "I have told Madame pretty well all I know," said the suave Italian, in excellent English; "but it is not much. Engstrom has engaged a room for a lady friend--a Madame Bohman." "Swedish also?" I queried, with a smile. "When does our friend expect Mr Thornton, as he calls himself?" "He is expected any moment," replied Luigi; "he has retained his room ever since he left for London." "Good!" I said. And we all three sat down and plunged into an intricate discussion of every detail concerning the suspects and our plan of campaign. My instructions to Luigi were to keep a constant watch upon the comings and goings of the Swedish engineer and his lady friend, while to Madame Gabrielle fell the task of endeavouring to scrape acquaintance with the latter on her arrival, in order to try to gain from some casual remark-- for we could expect nothing more--a hint of what was in progress. Engstrom's lady friend, Madame Bohman, arrived in due course, and, though she was quite unaware of it, we scrutinised her closely before we gave her a chance of seeing us. I saw at once that she was a complete stranger to me. Madame Gabrielle did not know her, and Luigi, with his faultless memory for faces, declared positively that she had never entered any hotel at which he had been engaged.