Based on Roy Horniman’s novel Israel Rank, A Gentleman’s Guide to Love and Murder finds Monty Navarro, a British commoner, discovering that he’s ninth in line to inherit the Earldom of Highhurst and electing to murder the members of the odious D’Ysquith family standing in his way. In the process Monty keeps a mistress, Sibella Hallward, and courts the comely young Phoebe D’Ysquith.