Percy's impact with the water does not hurt, and he sinks to the bottom soundlessly. He is also not wet and can breathe underwater. He mutters a thank-you to his father and finds his sword floating in front of him. A messenger that looks like Percy's mother appears, instructing him to go to the beach in Santa Monica before he goes to the Underworld. She also tells him to not trust the gifts, but disappears as Percy asks her to clarify.
He swims up out of the water and surveys the scene. People are talking about the events that just occurred, as well as seeing someone jump from the arch. He manages to find Annabeth and Grover and explains to them what happened, but not before a woman spots him and shouts about him being the boy who set off the explosion in the tower. They run and make it to the train station just in time to catch the train to Denver.
The next afternoon they reach Denver, a week before the summer solstice. Annabeth decides they need to contact Chiron, so she leads them to a car wash, where they pay to use a spray nozzle so they can "Iris-message," or IM. The spray mist makes a rainbow and Annabeth offers up a gold Greek drachma to Iris, the goddess of rainbows. An image of Half-Blood Hill appears, and Luke is the first person they see. He says that Chiron had to go break up a fight, and that campers are starting to take sides in the Zeus-Poseidon standoff and things are getting ugly. Annabeth and Grover go to deal with a car that pulled into the car wash while Percy finishes the conversation with Luke. They finish talking quickly as the mist fades and Grover and Annabeth come back, and Percy never does get the chance to talk to Chiron.
They head to a nearby diner for some food, even though they do not have money. The waitress is at first not going to let them order, but then a big man on a motorcycle comes into the diner, sits down with them, and says it is on him. Percy realizes quickly that it is Ares, god of war, Clarisse's dad. He says he wants Percy and his friends to do him a favor. He left his shield at an abandoned water park nearby while on a date, and he wants them to retrieve it. Percy says they already have a quest, but Ares says if they do it, he will tell him something important about his mother. Percy has no choice but to agree.
As they head to the water park, Grover and Annabeth explain that Ares's girlfriend is Aphrodite, goddess of love. They have had a fling going on for a long time, even though Aphrodite is married to Hephaestus. Hephaestus knows about it and always tries to embarrass them, which is why they meet in out-of-the-way places like this. The park is abandoned and not in good shape. They head for the Tunnel of Love ride, where Ares says he left his shield. They spot the shield in one of the boats, surrounded by mirrors so the gods could look at themselves. As soon as they reach for the shield, traps spring, and they realize that Hephaestus had made this trap to catch his wife and Ares together.
Cupid statues begin to weave a net around them and video cameras pop up, ready to broadcast them to Olympus. An army of wind-up spiders come at them, which scares Annabeth out of her wits. They try to fight them off, and Percy realizes the only way to get out is to turn on the ride and follow the water. Percy thinks as hard as he can, willing the water to begin to flow, and it does. The pool fills and they ride the current, jumping out before they smash into the gates at the end of the ride. They head out of the theme park, with Percy determined to talk with Ares.
Ares laughs at them when they return, admitting he knew it was a trap. He points them to a truck transporting circus animals and tells them this is their ride to Vegas. He also gives them a backpack with new clothes, some money in cash and drachmas, and some Oreos. He tells Percy that his mother is not dead, taken by Hades before she could die so he could keep her as a hostage and control Percy.
Percy, Annabeth, and Grover board the truck and see three circus animals trapped in cages, which makes Grover especially angry. They look miserable, and Grover promises them they will help them in the morning. Annabeth explains why she freaked out back at the water park: a woman named Arachne got turned into a spider because she challenged Athena to a weaving contest, and Arachne's children have been taking revenge on Athena's since.
Percy also realizes who Grover actually is: the satyr who tried to rescue Thalia, the daughter of Zeus. The other two half-bloods who Thalia befriended on the way to camp were Annabeth and Luke. Grover had been ordered to escort only Thalia to camp, but he could not bear to leave Luke and Annabeth behind, even though he knew it would slow them down. He blames himself for failing to protect them and for Thalia turning into a tree. Annabeth denies that he is blameworthy, as does Percy, and they commend Grover for his strength and heart.
After Grover falls asleep, Annabeth talks about her father, and Percy can see that she misses him even though she does not want to go back home and deal with his mortal wife. Percy wonders what will happen if a war breaks out, and if Athena and Poseidon take sides against each other. Annabeth says she does not know, but no matter what, she will fight beside Percy because he is her friend. Eventually they both go to sleep, and Percy dreams about the being in the pit again, having a conversation with his servant, a voice Percy almost recognizes. The being recognizes Percy's dream-presence and shows him an image of his mother, reaching out to him.
They wake up and the truck drivers come back to check on the animals. Grover reports that the lion says these guys are animal smugglers. Percy is able to speak to the zebra, since horses are within Poseidon's domain, and it asks him to open the cages and set them free. Grover places a satyr's sanctuary on them, ensuring that they will be safe wherever they go. The questers run away from the truck and into Las Vegas, where they find the Lotus Casino. In the casino, they are given the key to an enormous hotel room and told they can play unlimited games for free.
They immerse themselves in this place, and Percy only realizes something is wrong when he notices people dressed in clothes that do not match up with modern trends. He realizes that these people have been stuck here for years—one man thinks it is 1977, another 1985, and none of them realize how long they have been here. Percy finds his friends and pulls them outside, where they realize they had been inside the casino for five days.
Though Percy's mother has been a factor in his determination from the beginning, these chapters make it clear just how much his love for her has motivated him on this quest, and how willing Percy's enemies are to exploit this. Sally Jackson is the one person Percy has truly loved, the parent who was present in his life when the other was not. His visions of her in the river in St. Louis and in his dreams are a constant reminder that while he may not speak about her as often, his desire to get her back still influences his every move. The gods are aware of this and exploit it, with Ares bribing Percy to do his bidding with information about her and Hades taking her hostage, knowing Percy will come to retrieve her. The gods have found Percy's weakness, and they are clever enough to use it to their advantage.
Percy's dream visions have also come to prominence throughout this quest, and the conversations he overhears between the strange being in the pit and its servant reveal that there is an additional player in this conflict who Percy has yet to identify, making the problem much larger than it seems. Because this is a first-person novel, readers know only as much as Percy knows. We are in the dark as much as he is, wondering who this mystery antagonist is and what it wants. Each dream vision foreshadows dark events in the future, and Percy attempts to bear the burden of these dreams himself, unwilling to trouble his friends with much of what troubles him.
Before these chapters, Percy's only exposure to a god in human form was Mr. D, who is not a particularly imposing figure. Ares is the first god that Percy interacts with whose power is unquestionable, and Percy is unable to discern for certain whose side the war god is truly on. Ares is a modern-day embodiment of the qualities attributed to him by mythology: an aggressive, muscular, dark biker man with a love of conflict. He has no qualms with taking advantage of Percy, showing that he understands the role that tricks and manipulation play in any war. Even this brief interaction with Ares reveals that there are dynamics between the gods in this conflict that Percy cannot begin to understand.
One of the hallmarks of Greek mythology is that the gods, while they are immortal and omniscient, are similar to humans in their desires and behaviors. The secret relationship between Ares and Aphrodite is an example of this, as is Hephaestus, who is driven by the very human emotion of jealousy to try to embarrass his wife and her lover together. The gods are not so distant from humans that they do not feel human emotions—they are fallible, as is any mortal, which makes it easier for Percy and his friends to feel connected with them.
These chapters are important for Grover, who reveals a secret that he had been trying to keep from Percy: he was the satyr who failed to bring Thalia to Camp Half-Blood safely. As a character, Grover is extremely self-deprecating, blaming himself whenever something goes wrong. Having Annabeth and Percy around to reassure Grover of his worth is important—they both recognize Grover for his kindness, strength, and determination. Grover has shown strong resolve in his motivation to keep pursuing a searcher's license despite failure. Additionally, he has shown his compassion by spearheading the attempt to free the caged animals from the circus truck.
Percy has faced many tests throughout the quest so far, but the Lotus Casino in Las Vegas is an entirely new kind of challenge. Until this point, Percy has encountered obstacles that test his strength or skill. Now, he encounters one that is a test of sheer willpower, his strength to resist and use reason in a place that messes with his mind. The Lotus Casino also embodies the strangeness of time, showing that there can be a difference between perception of time and reality of time. If monsters have the power to bend time itself in this world, then there appears to be very little they cannot do.