“Last day of school. My mom was right, I should have been excited. For the first time in my life, I’d almost made it an entire year without getting expelled. No weird accidents. No fights in the classroom. No teachers turning into monsters and trying to kill me with poisoned cafeteria food or exploding homework. Tomorrow, I’d be on my way to my favorite place in the world—Camp Half Blood.

Only one more day to go. Surely even I couldn’t mess that up.

As usual, I didn’t have a clue how wrong I was.”

This passage from Chapter 1 fills in details about Percy’s past, linking where Percy begins his journey in The Sea of Monsters to the trials and growth he experienced in The Lightning Thief. Percy’s description of past troubles explores the types of trouble demigod kids face in the mortal world due to attracting monsters. Percy almost making it through an entire school year without an incident contrasts to past years, where he was expelled long before the year’s end. These paragraphs also foreshadow the trouble Percy encounters in The Sea of Monsters, as well as how Tyson’s presence over the last several months kept monsters away.

“Bull Number One ran a wide arc, making its way back toward me. As it passed the middle of the hill, where the invisible boundary line should’ve kept it out, it slowed down a little, as if it were struggling against a strong wind; but then it broke through and kept coming.”

These lines come during the battle on Half Blood Hill at the beginning of Chapter 4 and show how the border around camp is failing as a result of Thalia’s tree being poisoned. The bull here is a Colchis bull, a fire-breathing creature forged by Hephaestus (god of fire). Normally, the border around camp prevents monsters from crossing, but the weakened border allows the bull to pass.

“Annabeth shouted: ‘Tyson, help him!’

Somewhere near, toward the crest of the hill, Tyson wailed, ‘Can’t—get—through!’

‘I, Annabeth Chase, give you permission to enter camp!’

Thunder shook the hillside. Suddenly Tyson was there, barreling toward me, yelling: ‘Percy needs help!’ 

This quotation also comes from the fight in Chapter 4. Here, Tyson, a monster, is not able to enter camp. In contrast to the bulls who pass the border, if with difficulty, Tyson requires permission from Annabeth (a demigod).