Mr. Pottermack's Oversight by R. Austin Freeman

When, after breakfast on the following morning, Mr. Pottermack betook himself, rucksack in hand, to the walled garden, he experienced, as he closed the door behind him and glanced round the enclosure, curiously mixed feelings. He was still shaken by the terrific events of the previous night, and, in his disturbed state, disposed to be pessimistic and vaguely apprehensive. Not that he regretted what he had done. Lewson had elected to make his life insupportable, and a man who does that, does it at his own risk. So Pottermack argued, and he reviewed the circumstances without the slightest twinge of remorse. Repugnant as the deed had been to him, and horrible as it had been in the doing -- for he was by temperament a humane and kindly man -- he had no sense of guilt. He had merely the feeling that he had been forced to do something extremely unpleasant.

When, however, he came to review the new circumstances, he was conscious of a vague uneasiness. Considered in advance, the making away with Lewson had been a dreadful necessity, accepted for the sake of the peace and security that it would purchase. But had that security been attained? The blackmailer, indeed, had gone for ever with his threats and his exactions. But that thing in the well -- It was actually possible that Lewson dead might prove more formidable even than Lewson living. It was true that everything seemed to be quite safe and secret. He, Pottermack, had taken every possible precaution. But supposing that he had forgotten something; that he had overlooked some small but vital detail. It was quite conceivable. The thing had frequently happened. The annals of crime, and especially of murder, were full of fatal oversights.