Giant battle robots! Cotton candy betrayal! Blasts from the past! And the ultimate challenge to stay true to themselves and each other await Theo and Alexander in the final book in the tragic series about the Sinister-Winterbottom twins, who must solve one wretched mystery after the next, brought to you by #1 NYT bestselling author Kiersten White.

Trapped in Aunt Saffronia's spectral house, Theo and Alexander must work together to escape, stop their newfound nemesis Essa and her henchman Edgaren't, save Wil and their friends, find their parents, and maybe, just maybe, get things back to normal.

Following the clues left behind, the twins find themselves at Siren's Song Seaside Amusement Park. Old faces and new surprises await them in a park that was built to lure in visitors...and their secrets.

As they get closer to answers, the twins are left with the biggest question of all: Who is Essa really, and why is she so determined to find their parents?