Friendship.

Friendship is one of the main themes in The Son of Neptune. Friendship is what drives the characters to act and it is what makes the characters capable of supreme sacrifices. Each of the three main characters: Percy, Frank, and Hazel is changed by the support they receive from their friends and by the support they give to their friends.

Percy's biggest weakness is his deep love for his friends. It is stated many times in the book that his inability to hurt his friends will be his downfall. When Percy's memory is gone he is still driven by the feeling that there are people out there he loves and who love him. Annebeth is the only one he can truly remember, but he also catches glimpses of Gordon and Tyson in his dreams. Percy is quick to bond with Frank and Hazel and trusts them with his...