After being outed in the last novel as a spy, Megan, also known as Firefight, has departed, and now David Charleston, AKA Steelslayer, must find her. He sets off with Professor Phaedrus, AKA Prof. They must move in secrecy, so as not to attract the Epic who rules Babilar (a post-apocalyptic Manhattan). On their way, they encounter Regalia whom David is suspicious of. He wonders if his professor knows more than he is letting on.
In the ruins of New York, they find skyscrapers where people have made homes. They meet up with Val, a Reckoners operational leader. They also meet Exel, a kind, enormous man, and Mizzy, a sparky and chaotic technician. While discussing the pros and cons of the apocalypse, an explosion is heard from nearby buildings. An Epic has been sent to demolish the neighborhood. In the ensuing fight, they seek a weakness on the Epic to exploit. David spots bandages on his chest as the Epic, AKA Obliteration, thanks David for killing the foe from the last novel, Steelheart. Obliteration attacks and David finds himself sunk into water, trying to survive. The crew saves him in a submarine.
Exel and Mizzy help David to use water as a weapon using a jetpack. As they continue on, a side plot is revealed where Mizzy wants to kill Firefight for a killing she was part of. David realizes that Megan has been following them. He meets with her under cover, and they talk about strategy. He loves her and goes in for a kiss, but she pulls a gun on him. He notices the safety is on. He continues practicing with his water gun and studies about his enemies and their weaknesses.
They reencounter Obliteration. They seek the help of a shapeshifting Epic who can turn into birds and other animals. In the planning of a counterattack, the finally connect with Val and Prof. Megan and David connect in a following scene and finally kiss. She explains her secret magic powers to him. Val discovers them meeting and plans to use Megan as bait. Calamity, another Epic, arrives and David fights him with his water. In the battle, Megan is endangered, and he tries to save her. He arrives too late, discovering that in her dying, she set up a weapon that will mean ultimate victory in the story.
