To Michael's chagrin, a hacker has broken through his defenses and entered the STN-J's systems; a Witch's symbol is being broadcast from Robin's terminal. Meanwhile, Robin had spent the night talking to the mysterious old woman she met in the Walled City. Is she a ""Methuselah"", a Witch rumored to be immortal? And will Robin be able to accept what she is telling her?

Robin is surprised to learn that the Inquisitor who test her has arrived in Japan to test a new potential Hunter. As Robin watches the Inquisitor test the candidate, Shiro Masuda, she is reminded of her own inquisition. She finds that there is a thin line between being a Hunter or a Witch. Masuda must now choose which side he will join, and accept the consequences of his decision.

While on a case with Amon, Robin is ambushed by an unseen attacker. Later, back at the STN-J, Michael discovers that the shell casting left behind came from anti-Witch bullets. The weapon that could fire such bullets have not been used by the STN-J in five years. Who could be Hunting Robin?

Zaizen is trying to develop a new type of Orbo that would allow ordinary humans to hunt Witches, but it has disturbing side effects. Amon meets with Robin but does not attack her; instead he reveals more about his orders. Dojima and Nagira follow a Factory assault van but the target is Sakaki!

Robin and Amon finally confront Zaizen and learn the truth about Robin's existence. To Zaizen's surprise, instead of being traumatized, Robin is instead strengthened with resolve. Now Robin and Amon must stop Zainzen's final solution for the sake of both Witches and Humans alike.