The Prosecution of Mr. Darcy's Cousin

Fitzwilliam Darcy is enjoying his marital bliss. His wife, the former Elizabeth Bennet, presented him two sons and a world of contentment. All is well until "aggravation" rears its head when Darcy receives a note of urgency from his sister Georgiana. In truth, Darcy never fully approved of Georgiana's joining with their cousin, Major General Edward Fitzwilliam, for Darcy assumed the major general held Georgina at arm's length, dooming Darcy's sister to a life of unhappiness.
Dutifully, Darcy and Elizabeth rush to Georgiana's side when the major general leaves his wife and daughter behind, with no word of his whereabouts and no hopes of Edward's return. Forced to seek his cousin in the slews of London's underbelly, at length, Darcy discovers the major general and returns Fitzwilliam to his family.
Even so, the Darcy's troubles are far from over. During the major general's absence from home, witnesses note Fitzwilliam's presence in the area of two horrific murders. When Edward Fitzwilliam is arrested for the crimes, Darcy must discover the real culprit before his cousin is hanged for the crimes and the Fitzwilliam name marked with shame.