Sam tries to make Mohamad in to a worthy partner after he realizes his dark destiny. Scab and Ivory become daywalkers and return home to fin the Sisterhood destroyed.
Sam sitting on the edge of the pool at the juvenile detention facility, being as creepy as it is possible for a person to be and reflecting on what made him the horrifying man we see before us.
As you may recall, Sam's dad is almost as terrible as Sam is, having caused his son's deafness. Sometime after, we find Sam being checked into the very same detention center in which he recently murdered all those children. Teenage Sam's not having a very good day, so he decides to do what any kid in his position would and bites off his father's index finger. You know, like a totally normal, not at all future serial killer. At least we now know where he got that particular proclivity.
Meanwhile, Scab and Ivory are still alive and kicking, but they have run into some rather unfortunate characters. And we're not even talking about the jerks who are trying to pull them out from underneath some train cars. No, we're talking about the Daywalkers who murder the dudes and then tell Ivory they're going to make her into one of them, which they do by biting, because vampires gonna vampire.
In both the past and the present, Sam is haunted by this mysterious female figure shrouded in black who tells him this is where he will become who he is supposed to be, and that before he can do that he has to find the person who will stand with him. Naturally, he assumes this is Mohamad, who is also there and who is very very hungry. Sam decides this is when Mohamad is going to start his serial killer vampire training.
Young Sam was a bullied kid, of course, but there was a guard at the detention center who took pity on him. He wanted to teach Sam how to weld and work with his hands and told him that, while he could protect Sam inside, eventually he was going to need to learn to protect himself. Wrong thing to teach a kid like Sam who immediately decides this means he needs to beat the crap out of his bullies and then weld their teeth into ... jewelry? Back in the present, vampire Sam knows this little keepsake is the "thing he needs."
Back on the train tracks, Scab believes Ivory has been killed by the Daywalkers only to discover that she has been changed. She wants to change him as well and then return to the sisterhood to rule over them together. When they return to the sisters, however, they discover that their home has been burned to the ground and only a few sisters remain. Ivory turns them as well. This is probably not good news for humanity.
Speaking of humanity, it's been a while since we've checked in with the adorable human camp with all the little kids and their two gay dads. They're doing alright, though their spirits aren't very high. They need food and they're going to have to go out hunting. There is a debate about whether Felix should come along, and debate as to whether or not he is ready but decide to take him along.
Sam is being very strict with Mohamad's diet, not letting him eat animals. Not letting him eat anything, really. It's all an attempt to forge him into the same kind of person as Sam, which means going out and hunting for people. Like the people camping in the woods. Mohamad manages to hunt one down but Sam stops him from killing her because he will not feed like an animal. Felix manages to overcome his uneasiness about killing a deer and brings home food for the entire group, making him a hero.
Later that night, though, the tables get turned as Sam and Mohamad turn their attentions to the Johnsons and Mohamad corners Felix in the underground quarters. As Felix tries to convince Mohamad that he is just the latest minion of Sam, since Felix was forced to play that role last year. In the process, Felix manages to escape, and Sam decides he had it right before. He locks Mohamad underground and turns Felix into a vampire instead.
In the morning, Sam and Felix hunt down their food the way Sam was always hoping. And Sam receives one more visit from his angel of death. It is time. Whatever that means.