"I mean that Leon's father is your husband, Dr. Medjora!"
"Impossible!" Madame wished to disbelieve exactly what she had always suspected to be the truth.
"What I tell you is fact. I never do anything by halves. In the first place I had a hint of the truth from your own suspicions. You of course had little to go on, but you loved your husband, and when a jealous eye watches the relation between the beloved one and another, it will see much. I had no doubt that you had taken your idea from your observation of the love which the Doctor bestowed upon his protégé. Next I noted the coincidence of the dates. Margaret Grath appeared with the child a very few months prior to the death of Mabel Sloane. But I obtained substantial proofs."
"What are they?"
"Matilda Grath is an avaricious old woman. Her letter was in the nature of blackmail. She did not actually know that the Doctor is the boy's father, but she adopted that idea merely from the fact that he appeared upon the scene as soon as the guardian died. Then at the auction, it appears that there was a squabble over the possession of a collie dog, and the Doctor settled the dispute by purchasing the animal, and presenting it to Leon."
"Oh! He did that?" Madame was inwardly incensed, but she quickly suppressed any expression of her emotion.
"Yes! Old Miss Grath thought this was 'queer.' Then when she subsequently learned, what she did not at first know, that Leon had been taken into the Doctor's home, her doubts vanished. This accounts for her allusion to the Doctor in the letter, and the reason why she did not write again, was that she had no proof with which to substantiate her suspicions. I instituted a search, however, and unearthed a package of old letters in a worm eaten writing-desk, upon which no bid had been offered at the auction, so that it had been thrown into the waste bin in the barn. Among these I found two, which were from the Doctor, alluding to the boy, and also a photograph of himself sent at the earnest solicitation of Margaret Grath, as one letter explains. I suppose he thought that this was the least repayment he could make for a lifelong sacrifice."
"You have those letters?" asked Madame, with some anxiety.
"I have them here," answered the detective. "Do you wish them?"
"I do!"