"The Lightning Thief" is a fantasy-adventure novel written by Rick Riordan and published in 2005. Perseus "Percy" Jackson is the main character of the story whose best friend is Grover Underwood.
Grover Underwood had to bring his best friend, Percy, safely to Camp Half-Blood and he also had to protect him at his boarding school. What actually happened was that Grover lost Percy in New York City so Percy was the one who brought his best friend into the camp.
