Eleven-year-old Olive finds herself drawn to the grimoire of the witches who built her house and tries to use its spells to uncover the house's magic and control the cats themselves, but the book is more wicked than it seems.

When Olive Dunwoody takes her friends trick-or-treating, they're in for a shock--and being followed by an ominous creature is only the beginning. Strangers have come to Linden Street, and they seem awfully interested in Olive's house and in portals to Elsewhere. Can Olive trust them? -- from publisher.