Luke Fitzwilliam happens to share a London bound train carriage with Lavinia Pinkerton, an elderly lady who informs Luke that she is travelling to Scotland Yard to report a serial killer, responsible for the deaths of three people: Amy Gibbs, Tommy Pierce and Harry Carter, and that another man, Dr John Humbleby, will be the next victim. Luke, unsure of how to respond, feels that this is unimportant and pays lip service only.