Very early one summer morning, Lassair slips out of her Fenland village on a deeply personal mission and discovers the body of a young woman, hidden where it has no place to be. The girl's identity is quickly discovered but, as Lassair wonders who killed her and why, she swiftly becomes mystified and frightened.

Why did a sweet-natured and loveable little seamstress have to die? Did a lover kill her to keep a dangerous secret? Soon suspicion creeps uncomfortably close to home, pointing at the strange brother of the exotic foreign girl who is about to become Lassair's sister-in-law. Taken to Cambridge to meet an extraordinary man, Lassair learns more about the dead girl's past, and she believes she is beginning to understand.

Then another body is found and Lassair is filled with a dreadful suspicion. And who is responsible for the eerie, unearthly singing that she hears as night falls?