Answer:
The Battle of the Labyrinth is the 4th book in the Percy Jackson series, following the perspective of demigod Percy Jackson. The innocent 14-year old is up and ready to begin a brand new school year, but a calling from his second home, Camp Half-Blood draws him to discover that disaster strikes and monsters are attacking. Percy and his friends head on into the Labyrinth to save the world. Luke, son of Hermes, is using the Labyrinth to destroy Camp Half-Blood, and even worse, the Labyrinth often changes, leading to madness. With the help of a mortal, Rachel, they are successful, and find Daedalus, who is hesitant to help them. Even though its Annabeth's quest, the answer to getting through the Labyrinth lies in Percy. When the battle is over, Daedalus lets himself die, therefore closing down the Labyrinth forever.
Grover, Percy's friend, is also on his own quest. He must prove his existence, and find Pan. After finding him, which seemed near impossible, Grover comes back and bellows, and the sound scares the enemy away. This sound came from the part of Pan that now lived within him.
Happy learning!
--Applepi101