On a cold London morning in 1897, a young woman awakes on the ground outside the British Museum. She has no memory, and nothing that indicates her identity.
She does have a splitting headache, a lump on the back of her head, and a dim memory of having shot someone. She also quickly finds she has a talent for analyzing people's appearance and behavior for useful information that helps her survive. Unexpectedly, the police constable, John Kelly, who finds her decides that he trusts her. They piece together what they can, and then he's going off duty, and she's off to see what she can track down of her identity.