Emily and her friends must stop their enemies and save Earth from Jupiter's wrath when the CRU (Central Research Unit) begins cloning Olympians for their own profit. When Emily's father brings US newspapers back to Olympus with photos of a winning racehorse named Tornado Warning, Emily recognizes an uncanny similarity to Pegasus. She and several friends suspect the CRU (an independent research facility larger and more powerful than most people realize) has attempted to clone Pegasus – and perhaps other Olympians. Emily and her friends all know that Jupiter and his brothers, as leaders of Olympus, will not appreciate the CRU's abominable actions if Emily is right, and will likely destroy Earth (Emily's original home) as punishment, in spite of innocents not involved with the CRU.
Emily and several friends (Joel, Paelen, Pegasus, Chaosar the winged boar, and Alexis the sphinx) head to earth without Jupiter's knowledge and begin to investigate. When Paelen's winged shoes (which act like a GPS towards places or people) cannot find Tornado warning, they set out to find another friend, Earl. Earl is in hiding with a former CRU agent named Tomas who has turned good. With their approximate knowledge of Tornado Warning's whereabouts in California, the eight of them head west on the backs of those with wings. They pause in Las Vegas and establish a meeting place there if they are split up.
As they approach CA, Pegasus can sense his clone's presence and becomes disturbed, but leads them straight to the target. Pegasus goes crazy and kills Tornado Warning, but as he is an Olympian clone, Emily's powers heal him and bring him back to life – including the wings that were originally cut off to make people accept him as a race horse. (In a previous book in the series, Emily became the flame of Olympus and her powers include control of flame and healing, in addition to some new powers transporting objects that she doesn't quite have control over.) When the ranch owner and workmen try to take Tornado back, Emily firmly tells them no, and Alexis takes care of all who try to attack her.
With Pegasus' confirmed clone and new information from Tornado's former owner, the crew heads towards Area 51 to take care of the CRU's laboratory. Once there, they are split up by CRU agents and spies. Tomas is shot, and Earl is captured. Paelen, Josel, and Chaosar have some interesting but painful adventures involving more shooting spies and a cactus, and Emily (using her abilities from Pegasus' back) drives away the spies.
When the first group is slow to return to Las Vegas, Alexis, Emily, and Pegasus seek out a Nirad prince and his bodyguard to help them. When Paelen, Joel, and Chaosar reach the meeting place, they make a new friend (Frankie), explore and find resources, and get two of them (Paelen and Joel) into jail when a Paelen clone shows up. A wounded Paelen escapes to find Frankie in danger on their rooftop meeting spot. In the confusion, Paelen is knocked out a window over a 69-story drop and is caught by Chaosar, who flies him back to Olympus, where Jupiter ultimately realizes what's going on. Joel, meanwhile, is taken captive by some NRU guards.
When a hot-headed Emily arrives at Area 51 again with a hesitant Pegasus and Alexis in tow, she accidentally teleports her helpers into space, past Olympus. Thinking them dead, herself alone, and everything hopeless, she is led into the facility, but gradually realizes that the NRU's army of Nirad clones is drawn to her just as Olympians are. So are the Olympian clones. They will remain faithful to her, and with the help of Jupiter's army, they overturn the entire facility and free Joel, Earl, a badly-wounded Tomas, the cloned Nirads and Olympians. After a confrontation with Emily, Jupiter realizes he should not obliterate Earth, and together, they finish off the facility. Emily destroys everything, leaving a pit that Jupiter fills with water to create a lake. The remaining CRU agents are turned into Prometheus oak trees (an apparently painful fate) which will remain to provide shade. For survival, Tomas is turned into a willow tree (a much preferable fate to that of a Prometheus oak) and transported to Olympus, where he and Alexis will be able to stay together, as they have fallen in love. Their mission accomplished, the Olympians – their clones included – return to Olympus.
Best part of story, including ending:
I liked the world O'Hearn has created where Olympus, Earth, and the world of the Nirads exist alongside each other, with a method of transportation (the Solar Stream) between them, and some characters who are parts of both worlds.
Best scene in story:
In one scene, Alexis wants to go back to Olympus and tell Jupiter, but Emily refuses to go and insists on staying on Earth. Alexis knows Jupiter will want to destroy Earth, but that everyone will be upset if Emily goes down with it. Previously, Emily felt that Alexis had been forced upon her and her group as protection, but through this, Emily begins to see that she has more power than she thinks, just by virtue of who she is as the flame of Olympus. The same thing happens when she confronts and challenges Jupiter at the end; he reconsiders his desire to destroy Earth.
Opinion about the main character:
Emily is protective of her home planet, though quite the opposite when it comes to those who are cloning Olympians. She is quite clear on who the "good guys" and the "bad guys" are. She can sometimes get a bit upset / angry, however.