In Victorian London, race-walking, or 'wobbles', is all the rage. So on a Monday morning in November 1879, the crowds gather for Islington's bizarre six-day endurance walking race.
By Tuesday, one of the contestants is dead. Tetanus from a blister is assumed, but then there is a second death, and this time it's definitely murder.
A bemused Sergeant Cribb from Scotland Yard is called in, along with Constable Thackeray, and they soon discover that something foul is at play.