Ryana, a worthless girl-child, is sold to a mysterious woman who takes her to the home of the Shadow Sisters who are prized for their abilities as spies and assassins. She survives years of training in spite of being unconventional: adopting poisonous bats as familiars-something no one else would dare to do; choosing the blow dart as her weapon of choice—a weapon the Sisters don't teach; and relying on intuition rather than logic.
As she completes her training, the Shadow Sisters are under attack. The senior Sister selects Ryana to find out who is killing Sisters and why—because her intuitive approach has proved effective, even though her youth and inexperience makes it unlikely she will survive.
As she travels through the kingdom as a member of a gypsy clan, she finds the only way she can protect the Sisters and hope to discover the underlying plot is through ever more violence and killing. As she proceeds through the provinces, her secret enemies come to call her the Sister of Death and become desperate to find and kill her. But in her desperate fight to protect the Sisterhood and the kingdom, Ryana fears that she has destroyed herself and the only life she ever wanted.