Sueurs froides (S04E27)

Another Replika mission for our heroes. This time, as Ulrich and Aelita battle an indestructible giant new monster, Odd and Yumi are teleported to a base in Siberia, where they are faced with William, himself teleported there by Xana. Also, Ulrich bears the brunt of Yumi's fury, after avowing responsibility for a practical joke... of Odd's doing! (Prime Video)