"Let's be off. If I'm not mistaken, this is a business that requires immediate solution; and I don't believe I am mistaken."

He put his arm through mine, as we went down the stairs, and said:

"I know what everybody knows. Baron Repstein, the company-promoter and racing-man, whose colt Etna won the Derby and the Grand Prix this year, has been victimized by his wife. The wife, who was well known for her fair hair, her dress and her extravagance, ran away a fortnight ago, taking with her a sum of three million francs, stolen from her husband, and quite a collection of diamonds, pearls and jewellery which the Princesse de Berny had placed in her hands and which she was supposed to buy. For two weeks the police have been pursuing the baroness across France and the continent: an easy job, as she scatters gold and jewels wherever she goes. They think they have her every moment. Two days ago, our champion detective, the egregious Ganimard, arrested a visitor at a big hotel in Belgium, a woman against whom the most positive evidence seemed to be heaped up. On enquiry, the lady turned out to be a notorious chorus-girl called Nelly Darbal. As for the baroness, she has vanished. The baron, on his side, has offered a reward of two hundred thousand francs to whosoever finds his wife. The money is in the hands of a solicitor. Moreover, he has sold his racing-stud, his house on the Boulevard Haussmann and his country-seat of Roquencourt in one lump, so that he may indemnify the Princesse de Berny for her loss."

"And the proceeds of the sale," I added, "are to be paid over at once. The papers say that the princess will have her money to-morrow. Only, frankly, I fail to see the connection between this story, which you have told very well, and the puzzling sentence...."

Lupin did not condescend to reply.

We had been walking down the street in which I live and had passed some four or five houses, when he stepped off the pavement and began to examine a block of flats, not of the latest construction, which looked as if it contained a large number of tenants:

"According to my calculations," he said, "this is where the signals came from, probably from that open window."

"On the third floor?"

"Yes."

He went to the portress and asked her: