Summary
The book opens with Percy having a nightmare. It’s a stormy night and he's in a beach town, although he doesn’t know where. All of a sudden, he hears Grover approaching, murmuring that he has to "warn them". Grover, a satyr, is Percy's best friend. They saved the world together last summer, but Grover has been missing since he set off to find Pan last August. Now, he looks terrified, stumbling, running from a monster that Percy can’t see. He runs into a store called St. Augustine’s Bridal to hide from the monster chasing him, but the dream cuts off right before Percy finds out more. He wakes up, almost late for his last day of school, and tells his mom that he thinks Grover is in trouble. His mom reassures him that everything's fine but confesses that Chiron sent her a message that it might not be safe to go to Camp Half-Blood yet. Percy is confused, but when his mom urges him to go and meet his friend Tyson, he agrees since Tyson is sensitive and gets scared of the subway. Looking back, Percy, who is narrating in the first person, comments that although he didn’t realize it at the time, he wouldn’t be seeing his home for a while.
Percy goes to Meriwether College Prep, which is a special, progressive school. This is fine with Percy because of his ADHD and his dyslexia, but he finds the teachers can be a bit naive and let the students run wild. For example, one of the students, Matt Sloan, bullies Percy's friend, Tyson, a lot. As far as Percy can tell, Tyson is homeless. About six-foot-three, he gets picked on by everyone, while the school treats him as a sort of charity project. Strangely, however, social services can't find any record of him. Nevertheless, Percy does his best to defend Tyson, even if he has trouble looking past Tyson's crooked teeth. During social studies, Percy looks at a picture of Annabeth visiting the Lincoln Memorial that she sent him over the summer. He pulls it out every so often to remind himself that she's real and he didn't make the whole thing up. Seeing an opportunity to make fun of him, Matt takes the photo from him and hands it to a group of his friends, who all have strange names like "Marrow Sucker." Percy controls his temper, though, remembering he isn't supposed to fight mortals.
They split up in gym class to play dodgeball, and Tyson points out that the new kids smell strange, and when one of them calls Percy by his full name, he realizes they're monsters. It turns out they're Laistrygonians, man-eating giants. His coach isn't much help, and the giants block off both exits, preparing to kill him with fiery metal dodgeballs. Tyson pushes Percy out of the way and catches two of the balls, and hurls them back towards the monsters, killing them. It's mass chaos, but it occurs to Percy to run towards the locker room to get his sword. As he runs, the giants aim for him; when they miss and hit the locker room, the built-up gas in the room causes a huge explosion, and their belongings rain down on them. However, the last giant standing, Joe Bob, knocks Tyson down and is about to kill Percy, who still hasn't had time to get his sword. But then, he's impaled from behind by Annabeth, who looks very much the worse for wear.
After punching Matt in the face and telling him to lay off Percy, Annabeth confesses that she's been following him all morning and that they need to leave immediately, before vanishing with the help of her mother's gift—a Yankees cap that makes her invisible. Percy is left in the burning ruins, for which Matt Sloan blames him. Knowing he doesn't have time to explain, he grabs Tyson and runs after Annabeth. Annabeth is waiting for them and asks where he got Tyson from. She's creeped out by him but is surprised to learn that he's Percy’s friend and that he can talk. Her rudeness confuses Percy, but they can’t really focus on that. Annabeth confesses that she's been having bad dreams about camp, and Percy shares that he’s been having bad dreams about Grover. Monsters have been after Annabeth for days, but Percy’s been left alone the whole time. Percy explains the concept of half-bloods and the Greek gods to Tyson, who seems completely unfazed, except for his surprise at the news that Percy is the son of Poseidon. Annabeth rushes them, however, and pushes them to call a taxi for Camp Half-Blood. Percy still thinks she's talking about Tyson, but moves on.
Annabeth finds a spot to call them a taxi, except she does it using a golden drachma and speaks in ancient Greek, summoning a taxi from the asphalt. Although the three women driving the cab complain that they don't take Tyson’s kind, they agree to do so for extra pay, and the kids head towards Long Island. While they're speeding through New York, Percy realizes that the sisters, Tempest, Anger, and Wasp, only share one eye between the three of them. Percy is freaking out and Tyson is getting sick as the cab speeds over the Williamsburg bridge. Annabeth assures them that the Gray Sisters are quite wise, to which they reply that they know the location that Percy seeks. Percy demands they tell him and uses their eye as leverage when it pops out and falls on the floor. They yell out 30, 31, 75, 12—without explaining what the numbers refer to—and Percy returns the eye to them before they crash.
Finally, they arrive at the base of Half-Blood Hill and look up to the crest of the hill to see that the campers are under attack. They look up to find campers fighting metal bulls, but worryingly, the bulls are getting past Thalia’s tree, which normally guards the entrance to Camp Half-Blood against monsters. Clarisse, a daughter of Ares who's a bully and hates Percy because of his fight with her father, is leading the pack but is in trouble. Percy prepares to go and fight by himself, but Annabeth insists that they need Tyson, especially since the Colchis bulls are so hot that they're setting campers on fire. Percy however refuses and goes by himself. Clarisse is fighting hard but ultimately goes down, leaving Percy to try and save her. The fight continues, with Percy managing to get a blow in against one of the bulls, but he trips and ends up spraining his ankle. Annabeth shouts for Tyson to help him and gives him permission to enter the camp (usually, only demigods are allowed in). Tyson is immediately consumed by the flames from the bull but emerges unharmed, punching the bull in the face while Annabeth goes to check on Percy and give him some nectar for his ankle.
Percy is shocked that Tyson is alive. Annabeth then pushes him to look past the mist—a force that allows humans to see what they can process—and when he does, he realizes that Tyson is in fact a Cyclops. Annabeth explains that Tyson is likely a baby Cyclops, one of the homeless orphans. She calls them mistakes that don't always come out right and who then get tossed aside. Tyson being a cyclops is why he's immune to fire. They don't have time to dwell on that, though, because they have to deal with the aftermath of the fight. In talking with Clarisse, they find out that Chiron, their original activities director, is gone, while Argus, the head of security, was fired. Shocked, Percy wonders what happened, and Clarisse tells him that it’s Thalia’s tree. Six years ago, the tree was created when Zeus's daughter, Thalia, took her last stand on Half-Blood Hill to give her friends time to reach safety. As she was dying, her father took pity on her and changed her into a pine tree, with her spirit strengthening the camp's magical borders. But now, someone has poisoned her tree and those borders are weakening.
Analysis
From the very start of the novel, we can tell that there is something wrong in Percy's world. We learn quite quickly—or are reminded, for readers who have read the previous novel in the Percy Jackson series—that Percy has the ability to see what’s happening elsewhere in the world through his dreams. These dreams serve as foreshadowing for what might come next. Not only is Grover in trouble, but something mysterious is happening at Camp Half-Blood, leading us to wonder if Grover’s situation and the problems at camp might be connected, which is confirmed by Percy’s reflection that he won’t be home for some time after he leaves for school. School, for Percy, is still a complex place: while he’s known as a troublemaker, it’s clear that this has more to do with his ADHD and dyslexia than any actual malice. Despite Tyson’s uncertain origins and strange appearance, Percy has been determined to stick up for him from the very beginning.
Although he is limited in his ability to help Tyson, he makes sure to do what he can, including spending the school day with him and helping him get through the subway. Grover and Tyson aren’t the only friends he finds important either, as we see from the photo of Annabeth he keeps with him. Annabeth, for Percy, is not only a friend but also a representation of all the wild and unbelievable things that happened to him the previous summer. It would also be fair to say that Percy might have a slight crush on Annabeth, which Matt and his bullies quickly take advantage of. Nevertheless, Percy sticks to his guns and doesn’t fight since he believes they are mortals. Even though he’s not too fond of rules, Percy has a strong sense of fairness. This protective nature continues throughout the fight scene with the giants, with Percy’s main concern being to protect his classmates, particularly Tyson. Here, we get the first sense that Tyson might be more than what he seems after he smells the monsters coming and catches fireballs without being harmed. It also demonstrates how Percy has a tendency to be clever and obtuse at the same time. On one hand, Percy develops a really smart plan to defeat the Laistrygonians using the built-up gas in the locker room; on the other, he’s fairly cavalier about Tyson being able to survive fire.
Once Annabeth shows up, however, they all have other things to worry about. Annabeth, notably, immediately knows what Tyson is, but since the book is in the first person, we are limited by Percy’s perspective. A hint—which Percy doesn’t pick up on—is that monsters have been leaving him alone, while Annabeth has been hounded by them for weeks. Another one is Tyson’s familiarity with the gods and the way Annabeth talks about him, but Percy again chooses to focus on the situation at hand. The taxi they call is driven by the Gray Sisters, three women from Greek myth who gave the Greek hero Jason advice after he stole their eye and demanded their help. This old mythic trick is mirrored by Percy, who does the same thing when they mention they know the location he’s looking for. Mirroring Jason’s story foreshadows that much of this novel will take place at sea: like Jason and the Argonauts, Percy and his friends will be sailing through dangerous waters.
Arriving at Camp Half-Blood confirms their fears that something is wrong. While fighting monsters is, unfortunately, a normal part of demigod life, to see them invading Camp Half-Blood is scary, and it signals real danger. Narratively, we begin to understand that the main conflict of the novel will be about this invasion. Camp, which for Percy and the other demigods was for a long time the only safe space in the whole world to exist as a demigod, is no longer safe. It’s a serious enough situation that past conflicts—like the one between Percy and his former bully, Clarisse, who is fighting for her life at the top of the hill—are momentarily put aside. Tyson once again proves invaluable by helping them fight against the firebreathing bulls. It’s clear that Tyson is brave, even though sometimes he seems to be less socially aware than others.
The reason for that social awareness is clear once Percy realizes that Tyson is actually a baby—specifically, a baby Cyclops. Annabeth is strangely cruel when she refers to him as a mistake, something which seems off to both Percy and to the reader. Nevertheless, the fact that the gods often have children and don’t care for them isn’t news to either of them—Camp Half-Blood is proof that the gods are horrible parents who often don’t take care of their children. However, things at camp are changing for the worse. The absence of Chiron and Argus, who both care deeply for the campers, is already a huge red flag. But Thalia’s tree being in danger is a serious problem. Asides from protecting the camp in a symbolic sense, Thalia’s tree is also a symbol of the safety of Camp Half-Blood. Moreover, Thalia sacrificed her life for Grover and Annabeth so that they could be safe inside. Her tree dying is a bit like her dying as well.
