The Prisoner in the Opal by A.E.W. Mason — Read

Mr. Ricardo tried to push the crime of Suvlac altogether from his mind. Thus he would come fresh to its perplexities when once more his assistance was needed. He began his day to himself, accordingly, with a stroll through the Botanical Gardens, and without any intention came to the ornamental water where Le Petit Mousse, with its hand-driven paddle-wheels, was moored awaiting the holiday folk on the Sunday afternoon. At once he remembered the gabare and its patron, and his sly hints that the sloop would very soon belong to him without the necessity of paying for it. He stood stock-still, suddenly realising that he had told Hanaud nothing about that conversation. Hanaud was aware of the gabare, to be sure; Hanaud could have no doubt that it had left its harbour hours before the tide had turned, in order to sink the basket with the murdered victim in the middle of the broad river whilst the darkness still enveloped it. Hanaud could be trusted to look after the patron and his two sons. Yes; but his own unrelated conversation was vital. It had taken place in the afternoon, and the crime had been committed during the night which followed the afternoon. It proved, or if it didn't prove, it distinctly suggested, that the murder of Evelyn Devenish was premeditated. Mr. Ricardo turned abruptly away. This was certainly not putting the affair out of his thoughts. He walked out of the gardens and setting off any whither at a good round pace, found himself in a fine square and opposite to a magnificent old house, set back in a courtyard behind a long wall, such as nobles once inhabited and municipal officers use now.

"And what building is that, if you please? " he asked of a passerby.