Thusly named by her stepmother's accusation of being poisonous, Poison is a smart aleck girl that seems to enjoy little in her life except her baby sister. So, when one night, a scarecrow swaps her sister for a changeling, Poison knows she has to set out and rescue her sister. During this adventure, she meets loyal friends, a cat who is more than it seems, evil Phaeries and uncovers a murderous plan. This is the story of Poison discovering who she can be and then having to decide who she is as well.