Austin had left Halford and returned to it at such hours as would have just enabled him to reach the Abbey in the interval. Therefore, if he did reach it he could not have been at Luce Manor, and if he was not at Luce Manor he was innocent. Footprints were made at the Abbey by a certain pair of shoes. Those shoes were at Austin’s house every moment of the time from their purchase till they came into Tanner’s possession, except during the particular period in question. The tracks at the Abbey must therefore have been made during this period. Further, during this period Austin himself must have been wearing the shoes, as not only had he left his house and returned to it wearing them, but he had no others to put on—the remainder were all at his house. If, therefore, Austin did not himself make the tracks at the Abbey, he must have had no shoes during the time this was being done, in which case he could hardly have been at Luce Manor committing the murder. To Tanner the alibi was complete. Short of seeing Austin at the Abbey, he could expect no stronger evidence. Even if the truth of Austin’s story were unlikely, Tanner would have felt compelled to believe it. But, as he had seen from the start, it was by no means unlikely. On the contrary the whole thing was just the kind of plant the real murderer might probably enough devise to shift suspicion from himself to Austin. That it was such a plant Tanner now felt certain. And if so, had it not one rather suggestive point? The man who made the plant was familiar with Austin and his affairs. Who, of those who knew the affairs of both Austin and Sir William, had an interest in the latter’s death? The answer was not far to seek. One such at least was Cosgrove Ponson. He had both the knowledge and the motive. Tanner felt his next business must be with the cousin. And then a more sinister idea entered the Inspector’s mind. What if there was more in the plant than a mere attempt to shift the suspicion off the murderer? What if the plan was to encompass Austin’s death as well? If Austin were convicted and executed it would make a great difference to Cosgrove apart from rendering his position safe. Tanner recalled the terms of the will. If Sir William died Cosgrove received £75,000, but if Austin also should lose his life his cousin would net another £30,000. Here was motive enough for anything. Tanner recollected the woman who, Austin had stated, had handed him the note at the Old Ferry. As the latter’s story must now be taken as true, this must be a real woman, and if Cosgrove were the guilty man she must be his accomplice. Here was a line of inquiry which might lead to something. Tanner decided he would return to town by the next train, and start this new phase of the case. CHAPTER VI. What Cosgrove Had to Tell