The Battle of the Labyrinth

As Percy starts high school, the war with the Titans is no longer a distant threat. Kronos's forces have found a way to invade Camp Half-Blood from below, through the ancient Labyrinth of Daedalus, a shifting underground maze that connects to entrances all over the world.

If the enemy gains a guide through its twisting corridors, the camp's defenses will mean nothing. To stop them, Annabeth leads a small band, Percy, Tyson, and Grover, into the Labyrinth itself in search of its long-vanished architect, hoping to reach Daedalus before Luke does.

Inside, the maze warps time and space, throwing the questers against monsters, mad gods, and ghosts of the past while testing their trust in one another.

Above ground, Percy's mortal life grows complicated by Rachel Elizabeth Dare, a girl who can see through the magical Mist, and by the tangled loyalties of Nico di Angelo, who is chasing his own grief into the realm of the dead.

The fourth book deepens every thread of the saga, pushing its heroes toward harder choices and steeper losses as the final confrontation draws near. Action-packed and emotionally weightier than the earlier volumes, it sets the board for the war's last act while keeping Percy's voice warm, funny, and unmistakably human.