The novel begins a few weeks after it left off from the previous book. The group of adolescent fugitives are waiting for Evan Walker, one of their insider allies and Cassie's de facto boyfriend, at a prearranged rendezvous point should he have survived the blast at the end of the previous book. They are planning for the long winter ahead and decide on Marika (Ringer) to scout ahead in a cave complex which they intended to shelter at.
After she left, Alison (Teacup) goes after her and Ringer mistakes her as enemy. Ringer shoots and wounds her seriously, and by then, enemy choppers are already headed to their location. Ringer makes the tough decision of letting themselves get recaptured in order to save Teacup's life.
The duo are then transferred to another camp facility (as Camp Haven was blown up by Evan Walker in the previous book) where Commander Vosch reveals to Ringer that there have actually been no aliens or "downloaded alien consciousnesses" on the earth due to the risk it would pose and the Others are actually just enhanced humans with implanted memories. It is unclear whether any alien actually exist at all. The Others' goal is also unclear as it would have been a lot simpler to kill of all the humans on earth with "a really big rock" instead of going through the trouble of sending five waves of destruction. Ringer herself is then enhanced with The Twelfth System, which gives her superhuman strength and endurance, as well as nullifies her pain receptors.
Ringer and Alex (Razor, her caretaker during her enhancement) then proceed to break out of the camp and stay in an abandoned barn. They are later found by Vosch and Razor shoots Vosch in an attempt to give Ringer a chance of escaping.
Meanwhile, the rest of the group rendezvous with Evan Walker, who was nursed to health by a fellow Silencer known only as Grace after the blast. It is revealed that he is being hunted by her and that his own Twelfth System was overloaded and crashed, rendering him no longer enhanced. The group is later sent an IED by the Others. The IED is a 5-year-old girl with an explosive hooked to her throat. The explosive is calibrated to detect an increase in carbon dioxide levels, which means that the more people around, the more likely it will explode. Cassie manages to successfully extract it and contain it in a plastic baggie.
However, at this point, Evan Walker points out that if the Others see an explosion, they might think that they have been killed. They hatch a plan to use a carbon dioxide canister from the nearby diner to slowly leak carbon dioxide, causing the bomb to explode but giving them sufficient time to escape. Just as they are about to carry out their plan, Grace interrupts them and almost kills them all. The confrontation ends with Poundcake detonating the device with his own breath in an attempt to kill Grace and save the rest of the group.