Obviously the liability of humanity to err must be kept in view. At the same time it was difficult to see how a mistake could have occurred. The matter was not one of opinion, but of fact. Was Austin wearing the shoes when he went out and returned on the Wednesday evening? Were they clean before he started and muddy after he reached home? There did not seem to be any possibility of error on these points. More important still, were they worn at any other time? The butler had stated he always knew what shoes Austin was wearing, as all his master’s footwear was in his charge. It seemed to Tanner that if Austin was away from the house for so long as a journey to the Abbey would involve, in dirty weather, the butler would expect a pair of shoes to have been soiled, and would therefore be bound to know if those in question had been worn. But there was corroborative evidence which vastly strengthened the man’s statement, and that was the apparent age of the footmarks. Tanner could not tell to an hour when prints were made, but he felt certain he could say to within twelve. And in the case of these particular marks at the Abbey their appearance told him unmistakably they must have been made on or about Wednesday night. That the shoes came in wet and muddy that night, and that on Thursday morning they had dried by just the amount that might reasonably have been expected, was also strongly corroborative. The more Tanner pondered over the matter, the more he felt himself forced once more to the conclusion that the footprints at the Abbey were made on that Wednesday evening between the hours of nine and eleven. If Austin was now proved to have been at the boathouse between these hours, who then had made them? And again, if so, what shoes had Austin worn at Luce Manor? On that night the butler had gone over all his footwear, and all except the shoes in question were there in Austin’s room. Tanner was genuinely puzzled. This whole matter of the shoes seemed so clear and straightforward, and yet, if Potts and Miss Penrose were to be believed, it was all a fake. As he sat smoking after lunch in the corner of a quiet restaurant he kept racking his brains to find the flaw. But he could get no light, and he did not see just where to look for it. At last he decided he would try to trace Austin’s movements, from the time of his visit to Luce Manor on the Sunday evening previous to the murder, right up to the time he handed over the shoes to him, Tanner, on the following Friday. If Austin had arranged for a confederate to make the tracks for him he must have had communications with him, and it was possible Tanner might thus learn his identity. As he was in London, the Inspector thought he might as well begin with Austin’s visit to town on the Monday previous to the murder. Of that, the only thing of which he knew was the purchase of the shoes. He had noted the maker’s markings, ‘Glimax B 10735 / 789647S Hunt & Co.’