I don’t care much for Mr. Renard. He poses too much as the honest fellow rather puzzled by the course of events. His evidence, certainly supplied a fresh motive for Silverdale in the role of murderer. But Silverdale will not fit into the Heatherfield affair on any reasonable basis; and the tragedies at Heatherfield and at the bungalow are obviously interconnected. It’s a nuisance that Silverdale won’t tell us where he spent the night of the murders. It might save trouble if he did so. + 

“Justice” seems to be making a fool of himself. The fact that he forged Mrs. Silverdale’s writing in the advertisement addresses limits the circle still further. We now know: (a) that “Justice” must have learned of the bungalow shooting almost as soon as it was done; (b) that he knows hyoscine was in the Croft-Thornton stores; (c) that he is in possession of specimens of Mrs. Silverdale’s writing. + 

Markfield might fill the bill. + 

Other possibles are: Miss Hailsham, Miss Deepcar, and Silverdale himself. + 