Seventeen-year-old Sofi Snow already has a lot of responsibility. Since her father’s death and her mother’s dedication to her job as CEO of Corporation 30, Sofi has taken care of her younger brother, Shilo.
She is also the prime strategist for Corp 30’s team in the Fantasy Fighting Games. The games were developed by the different Corps, which has run Earth since the Fourth World War. The Delonese, an alien race whose planet now orbits the moon, also helped set up the games.
The games are violent entertainment, as well as a testing ground for new technology and are similar to a live-action video game. All participants are under the age of 18. Some, like Sofi, run computer programs that help alter their players’ suits and abilities. Others, like Shilo, navigate the actual obstacles in the arena.
The games began a year and a half ago and are held every six months. At the first games, Miguel, an intelligent and handsome teenager who served as an ambassador to the Delonese, broke Sofi's heart. In the second games, Shilo nearly died. This time, Sofi is determined to keep Shilo safe through the different game levels so their team can win. Winners receive a great deal of money that allows them to live well in a world where most people struggle to survive.
Miguel watches the games from his luxurious room on Level Three of the arena. Although an ambassador, Miguel is beloved by society for his good looks and celebrity antics. The only news, besides the games, that intrigues Miguel is that of the coming testing that will be able to detect if someone is fully human or has alien blood. At the moment, the Delonese are easy to distinguish because they are abnormally tall, at least 6 feet 5 inches, and they never blink. Although crossbreeding is forbidden, Miguel wonders if anomalies will appear with the testing.
As the games proceed, Sofi guides Shilo to win the first level. Miguel mingles with the audience and is suddenly aware someone has slipped something into his pocket. Finding a solitary place, he pulls out a piece of paper and discovers pictures that can be used to blackmail him, along with the order that he should make sure Corp 24 gets the blame, but he has no idea why or for what. The answer comes when a replacement player is announced for the next game level, which is made up of water. An explosion detonates and many children are injured or killed, either from the blast or by drowning.
Sofi manages to survive but keeps falling unconscious. The one thing clear in her mind is the fact that she saw Shilo on a stretcher, being cared for by a Delonese medical team. A mask is placed over Sofi's face, and she succumbs to a drugged sleep. There, she has a vision of Shilo being taken away in a dark spaceship. When she wakes, she finds she has been taken to the medical floor of Corp 30. She overhears Ms. Gaines, one of the heads of the Corp, giving instructions that once Sofi has been debriefed, she is to be killed. Sofi manages to escape with the help of a friend from the games, Heller.
Miguel uses his various contacts to investigate who survived the explosion and who set it off. His friend Claudius, another young ambassador, tries to help him figure out who sent the incriminating pictures. Miguel resists becoming anyone’s pawn and will not set up Corp 24 to take the fall unless they truly deserve it.
He is relieved to learn from his Virtual Intelligent assistant, Vic, that Sofi is still alive. Vic also says Sofi may have had something to do with the attack. After attending a meeting of different ambassadors and Corp executives, Miguel is again threatened, this time with physical assault, to blame Corp 24 or risk having the photos made public.
Sofi meets up with Heller, who helps her hack Corp computers. She accesses film of her brother in which the Delonese seem to be stalking him. She also learns that someone has made it appear that she orchestrated the bombing. She believes the only way to clear her name is to rescue Shilo, whom she thinks has been taken by the Delonese.
The only person she knows who has a shuttle to their planet is Miguel. Heller helps her crash a party Miguel is hosting so she can ask for his help. On the way to the party, she calls her mother to see if she has any information about Shilo and the Delonese. Instead, her mother begs Sofi to turn herself in to the authorities.
Sofi surprises Miguel at his party, and after talking together, she convinces him to let her and Heller pretend to stowaway on his shuttle, even though it could cause a war between the two planets. He wants to help, not only because he believes there is something nefarious going on between one of the Corps and the Delonese, but also because he still loves Sofi.
Before they can cement their plans, three men attack, hoping to abduct Sofi. The teens manage to escape, and Miguel arranges for Claudius to meet them at the shuttle bay. On board the shuttle, Sofi has another vision of her brother: He and other children are being led off a spaceship by the Delonese. Miguel comforts her when she wakes up in tears.
Miguel and Claudius manage to avoid an interplanetary incident by appealing to the Delonese’ sense of honor. The shuttle is allowed to land, and they are all treated as guests. The mixture of music, sculpture, painting and dancers that the Delonese display on their first night pleases Sofi.
When the aliens begin to chant together, Sofi’s wonder turns to distrust. Back in their quarters that night, they learn that the Fantasy Games are going to start up again in just a few days, even though the mystery of who caused the explosion is yet to be solved.
Sofi has another dream in which Shilo is crying out for her. She can hear his heartbeat and the beeping of a machine monitoring it. Then it stops. She wakes screaming, and Miguel comforts her again. Sofi is confused by her emotions. She welcomes Miguel’s innocent gestures of comfort, but she is still wounded from their previous relationship.
The next morning, Miguel and Claudius meet with the Delonese to be debriefed about the attack at the games. They hope to get aid from the aliens, but the Delonese are angry at the increased prejudices the humans are showing against them. Meanwhile, Sofi and Heller attempt to hack the Delonese computers to see if they can find Shilo.
An initial scan uncovers the unnerving fact that other than the capital city, there appears to be no other life forms on the entire planet. A friend from Earth sends up code from the new program being tested to show whether a person is entirely human or has been altered by the Delonese. When Sofi runs that code, she discovers that several large groups of unaltered humans are being kept within 500 yards of their quarters.
Then Sofi receives another message from Earth. This time, it’s the compromising pictures of Miguel. Horrified, Sofi decides to try and find Shilo without him.
An alarm sounds while Miguel continues to negotiate with the Delonese. They have reclassified Sofi and Heller as dangerous and will detain them indefinitely. Sofi and Heller will be taken for undisclosed testing. Miguel is not appeased when told that the testing will leave them mostly as they were.
Sofi and Heller return from an unsuccessful attempt to find her brother. Sofi confronts Miguel about the pictures she has seen. They show him with various young former gamers who have gone missing over the past two years. All the children are barely clothed.
Sofi believes Miguel has been selling the children to the black market. He insists that he happened across them and has been trying to help them. All of them went missing, then reappeared, with their memories erased. They all spoke a few words of Delonese, but when questioned by Miguel, went blank.
Sofi struggles to believe his story because of the pain he caused her. He admits he left her because he did not feel he was good enough for her. He has not been intimate with another person since they broke up, no matter what the news stories say about him.
As the two begin to realize they still care for each other, Heller interrupts them. A new computer program is showing that Delon is not a planet at all, but a space station. Shilo and the other humans are located beneath the surface. Sofi agree to make an attempt to escape the planet with the others before the Delonese arrive to take her and Heller in for testing.
Sofi has her Earth friends' help for navigation, and others through the space station, as if they were coaching her in a FanFight game. They find a room filled with human children, but none are Shilo. Claudius and a Delonese friend escort the children to a shuttle.
Sofi, Miguel and Heller keep looking for Shilo, and discover an ambassador from Earth has betrayed them. They continue their search and find a room filled with incubators. Human babies are being used to create Delonese children. Another room holds jars of hearts and lungs.
Sofi is sent a video of her mother and Ms. Gaines arguing. Gaines explains she had to orchestrate the explosion and have Sofi and Shilo killed in order to protect their relationship with the Delonese. Sofi’s mother admits she let the aliens test her children so she could help people, but she never thought it would cost the children their lives.
Sofi also gets information indicating that her friend Heller was involved in the cover-up. Sofi confronts him, and he admits his involvement. He believed he was helping all of humanity, but his primary goal was to save Sofi because he loves her. Sofi punches him and knocks him unconscious.
Sofi breaks down the door to another room and is immediately assaulted with memories of being in the same place, seven years ago. Miguel follows her into the room. His AI friend Vic sends him a video from seven years ago of a 10-year-old Sofi and her 5-year-old brother being tortured by the Delonese. After being subjected to a wall of scalding hot water, they are hit with freezing cold water. Then she is given a shot. Her body seems to stop working. As if everything inside her is being shut off by a switch.