Jason wakes up on a bus not remembering anything about himself or his past except for his first name. His friends, Leo and Piper, tell him they’ve been friends for a while in a boarding school. He takes out a gold coin out of his pocket but can’t remember why he has it. The teacher, Coach Hedge, tells Jason he is watching over two half-bloods that he was told to watch from the camp. Jason doesn’t understand why, but the words half-blood and camp seem familiar to him. On his field trip to the Grand Canyon, they went to the skywalk. A storm occurred and one of the kids, Dylan, turned into a monster. Jason took out his coin and turned it into a sword. He killed the summoned wind spirits and saved his friends while Dylan kidnapped Coach Hedge. After the storm ended, A chariot came and took the three kids to keep them safe. Annabeth told them that she was taking them to a camp to train half-bloods so that they could get stronger.
Leo and Piper are shown around camp. Leo takes a tour of many places in the camp, while Piper looks at cabins. She goes to Hera’s cabin and the Oracle, Rachel, shows upland grabs Piper, and tells her to free her from her prison. Piper then faints. Leo learns that he is a son of Hephaestus but is surprised because his mother died from a fire caused by himself. For some reason though, Jason calls Hephaestus, Vulcan, and many other gods their Roman names. While walking around, Leo thinks he saw his old babysitter while walking around and finds out that a mechanical dragon has gone crazy and put the head counselor of his cabin in a cast. He learns that the dragon has been going on a rampage and is destroying everything. The Hephaestus kids think that the dragon might be in the woods. Jason is talking with the camp leader, Chiron. He knows that he doesn’t belong at Camp Half-Blood but can’t remember why. Meanwhile, Piper is taken to the meeting room with Jason and Chiron. They come to the conclusion that it wasn’t a prophecy speaking through Rachel, but it was Hera. They believe someone is behind capturing Hera. Annabeth takes Jason to the cabin of the god of sleep to see if he can remember his lost memories but then finds out someone stole them. They suspect it’s Hera.
Piper recovers from her coma. Piper remembers the times she spent with her father. She keeps having dreams about a giant telling her to betray her friends in order to save her dad. After fully waking up, everyone goes to the campfire. Annabeth announces that she couldn’t find a missing camper named Percy. Later, they find out that Jason is a son of Zeus because he summoned thunder. The Oracle tells a prophecy of a quest for Jason. Piper gets claimed by Aphrodite and Jason chooses her and Leo to accompany him on his quest. While Piper was being claimed, Leo went to the forest to try to fix the agro dragon. Since he has the power to control fire, Leo is successful in fixing the dragon. The dragon then takes him to a secret place that only Hephaestus kids with the power of fire can open. He finds blueprints of ships. He also attaches wings to the dragon. He finds a magical tool belt that could make workshop equipment. He decides to come back later and tell everyone about the secret place after their quest.
Jason has a dream about Lupa, the wolf goddess, showing him the location of where Hera is and a dark figure rising right next to Hera. Lupa shows him how the place looks, but doesn’t tell him where or how to get there. He wakes up and tells Annabeth of his dreams. Annabeth then tells him to go to Boreas, one of the 4 wind gods located in Quebec City, Canada, to tell him where the place actually is from his dream. Leo comes out of the woods with his dragon named Festus. They decide to bring Festus with them because they can fly with him.
Jason and his friends go on their quest to save Hera. They go to Quebec City to find the god, Boreas. Boreas tells them to capture wind spirits and give them to Aeolus, the king god of the winds, to tell them where Hera is. When flying around, they all fell off the dragon and landed in a warehouse in Detroit. Piper was seriously injured so she was fed ambrosia to heal her. Leo went out to see if he could find Festus while Jason stayed with Piper. While trying to find his dragon, he feels left out because Jason and Piper are always together. He finds the dragon on many crushed porta-potties but also finds a half-awake woman that forms from the toilet water. The woman tells Leo that if he just walks away from his friends, she will help him but he throws a toilet paper roll at her instead. Meanwhile, Jason goes down to find Leo because he’s been gone for a long time. Piper gets worried and goes looking for Jason. Cyclops find Piper and tie her over a cooking pot next to Jason, who is also tied.
Leo runs back to find out that his friends are captured. He uses his wits and his powers to control machinery well to kill the giants. He frees Piper and Jason and they escape. They are in Chicago and find a wind spirit. They chase the spirit to be led to a sewer. The sewer led them into a store containing many things. Coach Hedge was in one of the cages frozen. The store owner, Medea, kept keeping Jason and Leo focused on the store items, but Piper wasn’t tricked and helped them to come to their senses. They save Coach Hedge who is actually a satyr, take some wind spirits, and escape, killing Medea. They find out that Gaea revived Medea, who was a girl in Greek mythology a long time ago.
After a long time of flying away, they fall off Festus again. This time they fall in a mansion in Nebraska. Festus breaks apart and Leo is sorrowful because he grew attached to it. They went inside and found that everything was gold. Gaea revived another person, King Midas, who had a curse that everything he touched became gold. King Midas uses his son to fight Jason. Since gold is a good conductor, Jason summoned a thunderbolt to destroy the mansion. Jason and his friends run away and arrive in Pikes Peaks, Colorado. They meet Artemis’s Hunters and they heal Jason and his friends. He sees a girl named Thalia and says that he is her brother. They discover that Jason is Thalia’s long-lost brother, supposedly dying after his mother abandoned him in the woods.
Jason tells the Hunters of his dream of Lupa. The Hunters knew where this was so they went there to see if they could help Hera. Jason and his friends now go to Aeolus to find out where Piper’s dad is instead of Hera. Aeolus tries to kill them but doesn't know why. Before Aelus can, Mellie, Aeolus's assistant, saves them and takes them to a cafe right next to the mountain where Piper’s dad is. While climbing the mountain, they felt like the ground was swallowing them. They know it’s Gaea who is doing this because she is the goddess of the earth and wants to trap Hera. They make their way to the top of the mountain and are thinking of a way to save Piper’s dad from the monsters.
Leo uses a little device he made to help him beat the monsters with Jason and Piper. They save Piper’s dad, though he is very fazed because he is just learning that Greek mythology is real. Piper is very worried about her dad. A few nights ago, Piper had a dream about her mom. She told her to give him an amnesia potion once they save Piper’s dad.
After giving Piper’s dad the amnesia potion, Coach Hedge offers to stay with him to keep him safe while the three go out to save Hera. When they go to Hera, they find out that Khione, Boreas’s daughter, was trying to kill them this whole time. She was the one who caused all their falls of Festus. Leo gets really angry and tries to kill her. Before Khione was hit with his fiery hammer, she escaped.
Looking around, Jason sees a giant rising from the ground. They realize Gaea wanted to reawaken the giant Porphyrion to destroy the world. Since Piper has an ability called charmspeak, an ability that allows her to convince others, she tries convincing Gaea to go back to sleep. In doing this, Leo was able to break open the cage that Hera was in without interruptions from Gaea. Hera scares away Porphyrion and Gaea away. They come back to camp. They find out the giants will go to Greece and destroy the original Mount Olympus.
The campers find out that there is another camp for Roman demigods. They believe that Jason is from there and their missing camper Percy, is there right now. Leo shows them the secret place in the woods and uses the blueprints for a ship. He also found the Festus’s head and attached it to the ship he was making. After they are done, they will set sail for the Roman camp, to unite and fight the giants together.