The same thing happened when the group was in prison. It had been one night and he had turned and attacked the group members that night. Everyone has the virus, turning into everyone. The person in the prison had not been bitten that they had not taken any precautions at night in him. Even if it is a normal death, everyone who dies will turn, even those who are shot with a gun will turn with a virus-free bullet. I'm a little confused in this episode, I need to find the prison episode and watch it again, but I don't remember. I'll edit my post again after watching it. Now just remember this about this chapter.
Review of Do Not Send Us Astray
