Timid Renata Molloy is in mortal peril after overhearing details of a breathtaking conspiracy. But her courageous and near-identical cousin Jane Smith—homeless and just two-and-elevenpence away from the workhouse—is willing to take her place if it means a roof over her head and plenty to eat. So Jane, with the help of Captain Henry March of Scotland Yard, whose hand in marriage she once refused, finds herself incognito at stately Luttrell Marches, enmeshed in a mystery of secret formulae, political plots, and a maze of secret doors and secret passages …