Sixteen-year-old Pilbeam may have made a terrible mistake. Living with her large family at 5 Brocklehurst Grove is wonderful in many ways, but remaining isolated from the rest of the world has become too much to bear. So Pilbeam decides that, whatever consequences, she will go to the theater, and the whole family's thrown into terrible danger. Pilbeam's encounter with a nosy neighbor threatens to expose the family's long-kept secret, and that could destroy them all. Sir Magnus, the family patriarch, declares a state emergency, making all members of the family virtual prisoners in the own home. But it may be too late. Because now Pilbeam's sister Appleby is rebelling, and even living under siege may not prevent the worst possible disaster from befalling the Mennyms.