S1·E15 Time to Say Goodbye

After the most recent attacks, the Team keeps Robin under careful guard at the STN-J. The only one absent is Amon, who can't be reached. As they analyze the odd shell castings left from the attack at Robin's apartment, they find that only three people could have fired the Witch bullet at Robin. Unfortunately, the prime suspect has been dead for years. With growing uneasiness, they realize the only other person that could do this is someone very close to them all.