A new pupil brings an unexpected, scaly companion to class. When a mysterious new student named Xtheres arrives at school, the children are intrigued. However, Xtheres harbors a secret: a large, slithering snake that he keeps hidden. The headteacher, Mrs. Grubb, is a stern woman with a particular dislike for anything that wriggles or bites, making Xtheres's attempts to conceal his pet a constant source of tension and potential disaster for the entire school.

This book is a typical offering from David Walliams, known for his humorous and often slightly mischievous children's stories. Readers generally respond well to his blend of silliness and relatable schoolyard scenarios, which often feature eccentric adult characters and brave, resourceful child protagonists. The narrative is designed to be engaging and funny for its target audience, with a focus on creating amusing situations and a satisfying, often chaotic, resolution. The book's reception is usually positive among its intended readership, who appreciate the lighthearted tone and the author's signature comedic style.