One of their own is stranded in San Francisco, a city long since claimed by the undead. When the rescue mission goes sideways and someone else is taken hostage by Abnormal zombies, Cate and the Alcatraz survivors find themselves pulled in two directions: Do they enlist the help of a doctor who claims to know the origin of the hyper-intelligent infected, or do they trust a mysterious group called the Organization, who have ties to one of Cate's people from before? In the Abnormal zombie camp, it's clear to Melody that her people are missing some crucial information about her captors. Can she get back to the island in time to tell them before they do something irreversible? With the island on the verge of chaos and the lives of their loved ones in the balance, the Alcatraz group clashes over who can be trusted, if anyone, and what to do about the Abnormals. To save her family, Cate must pick a side and confront the thing she fears most-before it's too late. In this twisting conclusion to the Abnormal/Variant trilogy, the survivors must reevaluate their ideas of family and humanity and finally answer the question that has been on everyone's mind since The End: What does Cate's immunity really mean?