The Last Olympian (Percy Jackson and the Olympians, #5)

by Rick Riordan

A minute later, the tree next to us shivered. Grover fell out of the branches, right on his head. “Grover!” I yelled. “Woof!” Mrs. O’Leary looked up, probably wondering if we were going to play fetch with the satyr.

GROVER I WAS SO WORRIED