Winnie Wednesday’s future is looking bright. Hemlock Falls is no longer hunting the werewolf, she and Erica Thursday are tentative friends, and Winnie finally knows exactly where she stands with Jay Friday.

With everything finally on track, Winnie is looking forward to the Nightmare Masquerade. But as Luminaries from across the world flock to the small town for the week-long celebration, uninvited guests also arrive. Winnie is confronted by a masked Diana and charged with an impossible task—one that threatens everything and everyone Winnie loves.

Winnie must stop these new enemies before time runs out, but her missing father is somehow entangled with her search for hidden witches, and as Winnie digs deeper into the war between the Luminaries and the Dianas, she discovers rifts within her own family she never could have imagined. What does loyalty mean when family and enemies look the same?