Witch Week tells the story of a world where witches exist, and the law dictates that all witches must be burned at the stake. The narrative unfolds in an English boarding school, where an anonymous note warns, "Someone in this class is a witch." This revelation causes a stir among the students of class 6B, especially a boy who has just discovered his ability to cast spells and a girl with a name reminiscent of a famous witch.

The story features the charming enchanter Chrestomanci, who also appears in other beloved works such as Charmed Life, The Magicians of Caprona, and The Lives of Christopher Chant. As the students scramble to identify the witch among them, alliances form and tensions rise, leading to magical mishaps and unexpected discoveries.

In this world of enchantment and danger, the students must navigate their fears and friendships to uncover the truth. Will they find the witch before it's too late, or will their society's harsh laws catch up with them?