What is chapter 13 about in the lighting thief

Chapter 13 of The Lighting Thief is about Percy Jackson, Annabeth and Grover finally reaching their destination: St. Louis. Once they reach the Arch, at St. Louis, they encounter a monster/Chimera. Annabeth and Grover make an escape, while Percy stays behind and thinks about falling into a fire-infested-hole. He gets set on fire, but manages to also set Arch in St. Louis on fire as well. The chapter ends with Percy jumping from the top of the Arch into the Mississippi River.