The deserted factory gets a new lease on life. Xana has taken over every last mechanism. In the silence of the empty Cathedral, the crazy computer is just waiting for our friends to walk straight into its trap. Odd and Jeremy find themselves in the Machine Room which is out of control and Yumi, Ulrich… and Sissi step into the elevator and right into the trap. The elevator plummets down and crashes on the ground. Yumi is the only one able to pull herself out of the debris to go for help from Odd and Jeremy who are ready to go to Lyokô. Sissi and Ulrich, whose arm is broken, are trapped at the bottom of the elevator shaft which is rapidly filling with water. Thanks to Yumi and Odd’s protection, Aelita manages to deactivate the tower just in time to stop them from drowning. Ulrich will have a plaster cast to remember this adventure by and also the memory of seeing a very different and unexpected side of Sissi.