he story begins with Percy recounting the story of Thalia and her great sacrifice in order to protect her friends. A young Annabeth, Luke, Grover and Thalia are running to Camp Half-Blood while being pursued by monsters. Thalia sacrifices herself to get the others into the camp and her father Zeus finds another way for her to live by transforming her into a pine tree, creating a magical border around the camp so that no other half-blood would suffer from a fate as she did. The scene then shifts to Percy during a camp competition against Clarisse La Rue. Percy loses the competition after he assists another camper, and is badgered by Clarisse. Soon after, Chiron and Mr. D investigate a Cyclops that has somehow passed through the border, and the Cyclops is revealed to be Tyson, Percy's half-brother. After the campers pick on Percy and Tyson, the camp is suddenly attacked by a Colchis Bull, who breaks through the border and ravages Camp Half-Blood. Percy finally defeats it with the help of Tyson, Annabeth, and Clarisse. Following this, Luke Castellan suddenly appears and confronts Percy, trying to convert the son of Poseidon to his cause. When Percy refuses, Luke disappears.