1941: As bombs fall on the city of London, Quentin Collins is reunited with his old friend, Rose. Trapped in an Underground station, she claims to have no memory of him. So he tells her how they met… 1906: Music hall star Rosie Fay is the talk of the town. But what connects her to the cases of spontaneous human combustion plaguing London’s ladies of the night? And why is Quentin so interested in the song she sings?