Mister Pück.When Aelita's dreams and hallucinations become too disruptive to ignore, the group heads to the Hermitage to discover their source. There, Aelita finds a doll she inexplicably recognizes to be Mister Puck. Hidden on this doll is a key to a train station locker, which contains the heavily encrypted diary of Franz Hopper. Upon its discovery, X.A.N.A. takes action, possessing Jeremy, to ensure they'll never be able to read it. When they deactivate the tower and Jeremy comes to his senses, Yumi explains to Jeremy why X.A.N.A. can possess him and not Ulrich, Aelita, Odd, or Yumi. They fight on Lyoko, which gives them more resistance to X.A.N.A., and since Jeremy has not gone to Lyoko in a while, even if he has already gone twice, he has less resistance, so Odd comes up with a way to give him more resistance. Jeremy is seen coming out of a scanner, with Odd and Ulrich coming out of the other two. Jeremy vows that that is the last time he sets foot on Lyoko because of a pair of Megatanks. Ulrich does not clearly state this, but it is believed that he is devirtualized by a Megatank.