Annabeth, Percy, and Thalia go to help Grover who was on a mission to find half-bloods, he needed help due to Dr. Thorn who will not let Grover near the brother and sister half bloods.
When Grover and his friends go to get the siblings Dr. Thorn transforms into a manticore, and tries to kill Percy and his friends. While in battle Annabeth falls of the cliff and is lost. The hunters show up and get rid of Dr. Thorn, before his helicopter of monsters shows up.
The hunters convince Bianca one of the discovered half-bloods to join them for immortality except in battle, as Percy disagrees. Nico the other new half-blood shows Grover his card game. As Thalia morns Annabeth.
As the hunters and hunters go to camp Zoe talks to Chiron about wanting to leave, Bianca abuses her power, and Percy and Thalia argue about Annabeth's death, Grover stops them from fighting.
Percy goes into his cabin and contacts his brother Tyson and talks to him about how his new job is going, through an Iris Message.
After a game of capture the flag that the campers lost to the hunters, The Oracle tells Zoe a prophecy giving 5 warriors a chance and 2 will die in the mission.