In the boys' locker room before gym class, Odd discovers he forgot to bring socks with him from his dorm. However, Kiwi soon arrives with a pair of socks in his mouth, much to Odd's delight. Meanwhile, at the track, tenth graders are running laps. While Yumi wins her race, the William Clone does not comprehend the idea of a race and does not run on Jim's mark, arousing Sissi's suspicions. Even after Yumi tries to distract her with a lie about dating William, Sissi remains skeptical.
At lunch, the Lyoko Warriors discuss the close call at the track, and Jeremie reminds them that the Clone's stupidity is out of his control. The others also encourage Yumi to keep up the façade of dating the William Clone to prevent other people from getting close to it. Jeremie then announces he has updated the security for the tower controlling the Clone, and asks one of the others to accompany Aelita to Lyoko while she installs the new programs in the tower. Odd volunteers, and also asks Jeremie if he can bring Kiwi to Lyoko, suggesting his superior sense of smell may be of use to them. Jeremie, however, categorically refuses Odd's offer.
After classes let out, Jeremie, Aelita, and Odd travel to the Factory, and it is revealed Odd has secretly brought Kiwi with him in his backpack. The trio also finds evidence of a motorcycle gang having been on the Factory's main floor. Meanwhile, in the dormitory building, Sissi confronts the Clone about its suspicious behavior, but Yumi arrives shortly afterward and takes the Clone out for a walk to get away from Sissi.
In the Scanner Room, unbeknownst to Jeremie and Aelita, Odd takes Kiwi into the Scanner with him when he is virtualized onto the Desert Sector. However, once he and Aelita arrive on Lyoko, Kiwi does not appear. As Aelita enters the tower to install the new security features, Odd worries about Kiwi, and begins to act strangely dog-like. On Earth, Sissi trails Yumi and the William Clone into town.
When Aelita finishes her work in the tower, Jeremie manually devirtualized her and Odd back to Earth. However, to Odd's horror, Kiwi does not return in the Scanner with him, and he continues to become more canine. Yumi then calls Jeremie and asks him to take over watching the Clone so that she may go home for the day. When Jeremie, Odd, and Aelita arrive back on campus, Odd's condition worsens as he is able to find a watch Jim had lost using only his sense of smell.
Aelita, Jeremie, and Odd meet up with Ulrich in his and Odd's dorm room, and Odd finally admits to taking Kiwi into the Scanner with him when he discovers he is growing a tail. Jeremie theorizes that Odd absorbed Kiwi during the virtualization process, and that the two of them are now fighting for control of the same body. He also believes he can separate them using the Scanners. Aelita calls Yumi, explains the situation, and asks her to stay with the Clone a while longer so that the others may return to the Factory to fix Odd.
Ulrich, Jeremie, Odd, and Aelita then travel back to the Factory, where they discover the biker gang has returned. The gang refuses to let the group into the building until Odd's canine behavior causes him to attack one of the bikers. Odd's condition frightens the gang, allowing the group to flee into the Factory and use the elevator. Jeremie then sends Odd to the Mountain Sector and begins unscrambling his and Kiwi's DNA.
However, the Superscan soon detects an activated tower in the Ice Sector, and Aelita and Ulrich are sent to Lyoko to deactivated it. When they arrive at the tower, they are immediately confronted by William and three Tarantulas, and a fight begins. Meanwhile, in the Mountain Sector, Odd is confronted by three Bloks, and is forced to flee so that he is not devirtualized; if Odd is devirtualized before Jeremie separates him and Kiwi, the fusion will likely become permanent.
Jeremie calls Yumi and asks her to come to the Factory. To keep Sissi away from the William Clone, Jeremie uses the Supercomputer to call her cell phone, and then uses a voice synthesizer program to impersonate her father and demand she return to campus. The ploy is successful, and Yumi travels to the Factory, leaving the Clone on a sidewalk bench.
In the Mountain Sector, the Bloks close in on Odd, and he is forced to fight back despite the danger. Yumi then arrives at the Factory, where she finds all the members of the biker gang have been possessed by X.A.N.A. Meanwhile, in the Ice Sector, William corners Aelita on the edge of a platform, planning to knock her into the Digital Sea. Ulrich intervenes after defeating the Tarantulas, but is quickly devirtualized by William, leaving Aelita alone.
After learning Aelita is in danger, Odd uses a way tower to travel to the Ice Sector to help her, despite the DNA separation still being incomplete. Meanwhile, in the Factory, Yumi is chased around the building's various rooms by the gang. While attempting to escape the assembly room, one of the bikers fires a bolt of electricity at Yumi, injuring her. No longer able to run, Yumi resorts to hiding, and barricades herself in a side room. In the Ice Sector, Aelita duels with William before making a break for the activated tower. However, William beats her there using his Super Smoke ability, leaving Aelita cornered.
Odd then arrives at the tower as well and intercepts William, allowing Aelita to enter the tower. As Odd battles William, the bikers manage to break into the room Yumi is hiding in and attack her again. Just as Jeremie finishes unscrambling Odd and Kiwi's DNA, Odd is devirtualized by William, and he and Kiwi return to Earth in separate Scanners. Aelita deactivates the tower, and the bikers all unconsciousness as their possession is lifted, saving Yumi. The Lyoko Warriors work together move the bikers, still unconscious, to the bridge and coat Kiwi's mouth with toothpaste. When the bikers wake up, they assume Kiwi is Rabid and flee the Factory.
The next day, the group meets in the courtyard, where Yumi tells Sissi she has broken up with William, and explains away the Clone's stupidity as William's way of sulking. Odd then wonders if he still has Kiwi's superior olfactory sense, as he can smell beef stew and Brussels sprouts in the cafeteria from all the way across the courtyard.
- The original French name for this episode is Kiwodd, a portmanteau of Kiwi and Odd's names.
- This is the first and only time an animal is brought to Lyoko.
- When Sissi enters William's dorm, one of the posters on his wall appears to be the original movie poster for the 1971 Stanley Kubrick film A Clockwork Orange.
The original episode summary can be found here.