Pa is off again to work on his world-changing scientific discovery, leaving the rest of the Coggins family behind at their hidden clifftop home, Dizzy Perch. Oliver is in charge, with strict instructions about no visitors, in order to protect Pa’s top-secret location. But Ma doesn’t listen, and invites her favourite author to say. When a woman arrives at Dizzy Perch claiming to be the author, the whole family are enchanted by their guest. All apart from Oliver, that is. A good job too, because the woman is really the sister of Pa’s Sworn Enemy Mac, whose mission it is to bring Pa down and steal his research. How is Oliver going to be able to keep his promise to Pa and protect his family, when they simply refuse to listen to him?