Mirany is the youngest of the Nine, the Archon, the living God of this Ancient Egyptian- like land. The Archon then dies to bring rain, and a new Archon must be found. The Speaker, the leader of the Nine, is corrupt, and plots to place a false Archon. Together, Mirany and the old Archon's musician, Obler, must place the true Archon on his rightful throne.
The book is set in the future, where America is a ruin and cities on wheels prowl the northern ice caps, the smaller ones look for trash as food, and the larger ones look for smaller cities as food. The protagonists, Hester and Tom, are not officially married. They are aviators of an airship. During one of their voyages they pick up Professor Nimrod Pennyroyal, a famous historian/novelist. On that same voyage, a mysterious group called Green Storm attacks the trio. Hester, Tom, and Professor Pennyroyal manage to survive, but their ship is going to crash.
Gregory recieves a strange invitation from his weird Uncle Max, instructing Gregory to come visit him in Vermont and bring "a companion." When they get there, Uncle Max picks him up in a horse-drawn carriage. When they reach Uncle Max's house, they find an old game board entitled "The Game of Sunken Places." Later they find an old egg timer bearing the same name, and when they flip it over, a trumpet sounds, and the Game begins. They meet many strange creatures, including a troll, an ogre, two warring fairy nations, and mechanical servants.
Gregor, whose father went missing several years before, is babysitting his little sister when she opens a grate in the basement floor and falls into the Underland, far below the Earth's surface. There he meets rats, bats, beetles, spiders, all of which are man-sized, and men who traveled down below the surface hundreds of years before. He tries to leave and fails, but hears word of his father. He then sets off in an adventure that, hopefully, will allow him to save his father and all the other humans in the Underland.
