But completely to prove this theory it would be necessary to show that Austin was at the Abbey at some time other than that he had stated. It was with this object Tanner was returning to Halford. He made most persistent inquiries, but was unable to find any evidence on this point. None of the cottagers nor farm hands in the vicinity of the Abbey had seen Austin, either on the Wednesday evening or at any other time. Nor had any other stranger been observed. If, however, Austin had been to the Abbey in the middle of the night, as Tanner suspected, the failure to see him was not surprising, and did not invalidate the main conclusion. On the contrary, Tanner believed he had solved his problem. Austin, he felt, was guilty beyond a shadow of doubt. And then Tanner saw that this solution cleared up another point by which he had been somewhat puzzled, namely, Austin’s readiness, indeed almost eagerness, to tell of his visit to the Abbey. That, he now saw, had been a trap, and he, Tanner, had walked right into it. He saw Austin’s motive now. From the latter’s point of view it was necessary that Tanner should inspect the footprints while they were still fresh. If some days passed before suspicion was aroused, the marks would have become obliterated, and the alibi worthless. Austin was a cleverer man than the Inspector had given him credit for. By his manner he had deliberately roused the latter’s suspicions so that his alibi might be established while the footprints were clear. That evening Tanner made careful notes of the evidence he had accumulated against Austin Ponson. When the document was completed, it read: