In 1840, the theatre world in London is shocked by the brutal killing of one of its youngest and most successful entrepreneurs, bludgeoned in his house. The discovery of a contentious theatre contract, a collection of promissory notes and a walking stick, its bloodied ivory head in the shape of a dog, are the only leads. Inspector Owen Endersby, of the recently formed London Detective Police Force, is called upon to apprehend the culprit before Christmas Eve. The inspector has six days to chart the "by-ways of the Criminal Mentality." The case soon involves street vendors, downstairs servants, money lenders and the greatest performers of the stage. Who had motive to batter the young man to death? Without the techniques of the modern-day detective, Inspector Endersby must root out the villain any way he can--by disguise, break-and-enter, bribery, mail tampering and physical force.