Abbey is a sixteen-year-old girl living on an alien world. Her sole companion is Scut, a genetically engineered symbiote called a Gnoph which lives in her left lung. Gnoph were designed to give superhuman powers to the host... but without access to her homeworld's medicine, they will both soon die. Attempting to transport back to her world, Abbey winds up on a medieval planet instead. There she makes the acquaintance of Duke William of Klag, a somewhat inept and cowardly young man. Will's fate becomes entwined with Abbey's when Scut lays an egg inside of him. With both their lives now at stake, they proceed to Abbey's world, which on the surface is not dissimilar to our own. But as Secret Police hunt them down, they have to fight to survive.