During Percy's (who is actually the son of Poseidon) training at the private camp of Half-Blood hill with other demigods like himself, his trainer, the satyr Chiron, who has previously disguised himself as Mr. Brunner, the Greek mythology teacher at Jason's school, also tries to protect the Half-Bloods from the Monsters.
But, before Percy arrives there he is on a field trip to a museum from his alternative school with his friend Grover and bizarre things occur. Mrs. Dodd transforms into a monster and attacks him; Mr. Brunner tosses him his pen which turns into a sword with which Percy defeats Mrs. Dodd. But, the next day she looks again like Mrs. Dodd. In Chapter 3 Percy returns home, happy to see his mother who tells him they are going on a vacation to Montauk where they will stay in a cabin on the beach. Grover mysteriously appears, and shortly after they arrive, their rest is interrupted by roaring outside and Percy's mother cries "Hurricane," which shocks Percy because they are on Long Island. But, Percy's mother insists they flee. More bizarre things occur as Grover's legs are furry and his feet become hooves. Then, their car mysteriously explodes after his mother swerves to dodge something dark. Percy refuses to believe that the car actually exploded, reasoning instead,
Lightning. That was the only explanation. We'd been blasted right off the road. Next to me in the backseat was a big motionless lump. "Grover!"
After a hairy monster, part bull, comes at him and his mother dematerializes, Percy passes out and awakens in a cottage, leading him to think he has dreamed strange things. When he looks at Grover, he notes,
Grover was leaning against the porch railing, looking like he hadn't slept in a week. Under one arm, he cradled a shoe box. He was wearing blue jeans, Converse hi-tops and a bright orange T-shirt that said CAMP HALF-BLOOD. Just plain old Grover, Not the goat boy.
"We put Mist over the humans' eyes," Grover has told him. This "Mist" is Percy's explanation of the lightning and his dreams.
Inversely to Percy's rationalization of what has happened to him, mythology helped explain to primitive man natural phenomena. For instance, Zeus was believed to hold thunder and lightning. Also, three huge gods called the Hekatonkheires, controlled hurricanes and terrible storms; they summoned this destructive weather from the pit of Tartaros. These gods were believed to possess a hundred hands and fifty heads which enabled them to wield such destructive power.