R. Austin Freeman 
Mr Pottermack’s Oversight [PDF ebook] 

Mr Pottermack is a law abiding, settled, homebody who has nothing to hide until the appearance of the shadowy Lewison, a gambler and blackmailer with an incredible story. It appears that Pottermack is in fact a runaway prisoner, convicted of fraud and Lewison is about to spill the beans, unless he receives a large bribe in return for his silence. But Pottermack protests his innocence, and resolves to shut Lewison up once and for all. Will he do it? And if he does, will he get away with it?