It's nearing the end of the year and Jeremie's research has hit a dead end. After the group collects some data from The Carthage Region, he plans to use a tower to decipher Franz Hopper's diary. Before the mission, Odd gets a message from a mystery girl. When he goes to meet her, he is attacked by one of Xana's ghosts and locked inside a well at the Hermitage. The ghost then assumes Odd's form and goes to Lyoko in his place. The tower that Xana activated to make the ghost then deactivates, confusing Jeremie. Putting it out of his mind, he begins his plan to decipher the diary. Shortly after they begin, the ghost turns on the group, devirtualizing Yumi and chasing Ulrich away from the tower as three Tarantulas arrive to protect it. At the same time, Xana attempts to take over Jeremie's tower, locking the decoding procedure so they can't abandon it. Jeremie realizes the true nature of the ghost during the fight, and Yumi goes off to find the real Odd. After the ghost proves to be ineffective against Ulrich, it shape-shifts into a clone of Ulrich. In this form, it proves to be an equal match for him. After much fighting, Ulrich finally beats the clone, but is taken out by a Tarantula shortly after. Just when it looks like Jeremie's tower will fall, Franz Hopper steps in and protects it. The diary then decodes fully. After examining the diary, Jeremie tells Aelita that she is Franz Hopper's daughter.
