It continues the story of Arthur Pehaligon and his quest to fulfil a mysterious Will in order to reclaim an otherworldly House from seven antagonistic Trustees.

Following the events of the previous novel, Arthur must secure the third part of the Will from a fiendish pirate in order to save the Border Sea from Drowned Wednesday's insatiable appetite.

Picking up after the events of Grim Tuesday, Arthur discusses Drowned Wednesday's invitation to meet for lunch with Leaf while he is hospitalized.

Sunscorch commands Dr. Scamandros, an Upper House Sorcerer and the ship's navigator, to open a transfer portal to elsewhere in the Secondary Realms.

Arthur meets with Wednesday, who explains that she regretted her part in defying the Will, especially since doing so afflicted her with gluttony and turned her into a leviathan with an insatiable appetite.

Although they experience navigational difficulty, they are eventually able to enter Wednesday's stomach and the worldlet therein, which is in the form of an island.

There, Arthur and Suzy, disguised as rats, find several of Feverfew's escaped slaves, who have been hiding in a remote cave on the island and formed a religion around a Carp.

Lady Wednesday is healed from her gluttony but she dies, having been poisoned by the worldlet, which had opened a void to Nothing.

School Library Journal called it "[a] must-have for anyone who has the first two entries in this well-crafted, exciting series" and VOYA magazine said, "Nix is endlessly inventive, and his latest book is another thrill ride.

"[3] Booklist was more mixed, praising the imagination of the series but said that "experiencing it can be at once exhilarating and overwhelming," and noted that new readers could find the book "frustratingly esoteric.