In the year 2080, a post-apocalyptic world is plagued by the Undead Virus, which has turned most of the population into zombies and ghouls. Breelynn, a 27-year-old military scientist, resides in Subterra Nova, a subterranean city built to protect people from the virus and radiation. Bree's father, a high-ranking officer in the colony's defense force, raised her in a military family. Although she became a skilled fighter by 18, she decided to pursue her passion for science, training to become a scientist after her older brother became the colony's First Commander. Bree's determination to find a cure for the Undead Virus stems from her loss of her father. She is driven to find a cure for the virus and prevent others from suffering the same fate. Bree raids an illegal lab one day and finds Hope, an eight-year-old half-ghoul girl with unique abilities. The ghouls want Hope, so they raid Subterra Nova, hoping to distract Bree away from Hope. Hope is taken by the ghouls, and Bree decides to find her. While searching for Hope, Bree meets Treyson, a 30-year-old man born a ghoul. Treyson and Bree fall in love as they work together to find Hope. Treyson had a difficult childhood, being rejected by his human family for being a ghoul. Despite his tough exterior, he has a kind heart and is fiercely loyal. Meanwhile, a war is brewing between the Ghouls and humans. The colony is being betrayed by a woman whose son is a ghoul. She is secretly telling her son all about the colony, which is relaying all the information to the Ghoul leader, Bryndon, who is secretly Bree and JR’s uncle. Bryndon and Bree's little sister Zoey, who is now 20 years old, are leading the Ghouls. Bree and Treyson face dangerous challenges while searching for Hope. They meet new allies and enemies along the way, leading to a climactic battle between Bryndon's army of Ghouls and Subterra Nova's defense force. Eventually, Bree and Treyson find Hope and return her to Subterra Nova. However, the war between Ghouls and humans intensifies, leading to a final showdown that determines the fate of the colony.