‘No, sir. He is a bookseller’s assistant in London—to Evans & Hope, in Paternoster Row. His people live here, and he was down on a couple of days’ holidays.’ Tanner noted the address. ‘How was Mr Austin supposed to be dressed?’ ‘In bluish grey clothes that looked like flannel, and a white straw hat.’ ‘And Sir William?’ ‘In a black cape and felt hat.’ ‘They didn’t see either of them leave the boathouse?’ ‘No, sir. They were passing on down the river towards the girl’s home.’ Tanner was silent. If this news were true, though he could hardly credit it, the alibi must be a fake after all, and Austin must have duped him. And yet, how could it be a fake? He had tested it thoroughly, and he had been satisfied about it. He did not know what to think. ‘Why did this girl not come forward before?’ he asked. ‘She didn’t know till she read the account of the inquest that there was any question of foul play.’ Inspector Tanner was considerably perplexed. The more he thought over what he had just heard, the more disposed to believe it he became, and at the same time more puzzled about the alibi. But one fact at all events appeared to stand out clearly. If Austin had really been to the boathouse that night, it surely followed that he must be guilty of the murder? His presence there would not of course prove it, but would not the alibi? If he had merely omitted to mention the visit it would have been suggestive, but if he had invented an elaborate story to prove he was not there, it undoubtedly pointed to something serious. But, as had always happened up to the present, his own next step was clear. He must see the girl and hear her statement himself, and afterwards visit Potts, the bookseller’s assistant. If he was satisfied with their story he must once again tackle Austin’s alibi and not drop it till he either found the flaw or was so convinced of its soundness as to conclude the new witnesses were lying. Next morning he was early at the grocery establishment of Mr Thomas Smithson, in close conversation with a tall and rather pretty girl in a cream-coloured blouse and blue skirt. She repeated the sergeant’s statement almost word for word, and all Tanner’s efforts could neither shake her evidence nor add to it. She was quite sure the man in the boat was Austin; she had seen him scores of times; he was a well-known Halford figure. So was Sir William; she had seen him scores of times also. No, it was not too dark to see at that distance; her sight was excellent, and she was quite certain she had made no mistake. She was very shamefaced about the cause of her presence on the river bank, and begged Tanner to respect her confidence. He promised readily, saying that unless absolutely unavoidable, her name would not be brought forward.