In book three of the Percy Jackson and the Olypmians series, everything starts out as quickly as in the other novels. Grover has been following up on a couple of potential half-bloods at a military academy and needs Percy and Thalia’s help. He also brings along Thalia, the daughter of Zeus, who sacrificed herself to make sure Luke and Annabeth could get to camp, but was rescued from the tree by the Golden Fleece.
The two half-bloods are Nico and Bianca di Angelo. Little is known about them and as the story progresses Riordan drops little hints that they have some how fallen out of time for a long period of time, such as asking Bianca who the president before last was and she says Roosevelt. They are able to get Bianca and Nico from the school, but Bianca is offered to join the Huntresses of Artemis and accepts the position abandoning her brother to Camp Half-Blood. In the process however Annabeth disappears and is ultimately held hostage by the Titan Atlas. She takes the weight of the sky on her shoulders to supposedly save Luke, but this doesn’t work. The goddess Artemis is later tricked into taking the sky from Artemis.