The episode begins with the spies are pursing evil magician, Dash Dawson. However, he manages to get away, but not before Clover blasts his wing that sends him falling to a bridge. Alex tries to save him, but Dash falls. Sam has decided to sent WOOHP to look for him.
In the next morning, the spies are sent to their school in the science lab for a pop quiz. After class, they find Arnold trying to be a president and Mandy taunts him that he will be King of the Nerds if he's the president. By the time, she leaves with Sam and Alex, the ring that Dash has left falls into the floor and Arnold gets it.
In the gym, the spies are playing a game of dodgeball when Arnold appears. He dodges the hits his opponent sends, and hits him back. The spies have a feeling that Arnold is acting strange. Upon seeing this, Mandy begins to have thoughts of voting for him.
Just then, the trio is sent to WOOHP by Jerry to tell them that Dash is not in the waters and he is at large. Also, he tells them about the Cat's Eye emerald, a ring that has special powers, and to be careful of Dash because he might be back for revenge.
Meanwhile, Mandy is talking on the phone at a hallway when she is attacked by a mysterious person in a room. When the spies go to her rescue, Mandy is turned into a nerd and must leave before someone sees her that way. The spies have manage to find her scrunchy.
In their villa, the spies are relaxing by the sun. Sam thinks that Mandy is just begging to get attention again and that she's a drama queen. Clover thinks that Mandy has bad fashion advice and leave to put on sunscreen lotion. Just then, Arnold arrives and uses his ring on Clover.
By the time Sam and Alex go to the rescue, Clover is turned into a nerd. When being asked what happened, she replies that Arnold has used a green ring to turn her into a nerd, and Sam realizes that he has the Cat's Eye emerald.
Just then, Arnold escapes and the spies pursue him. He tries to use an incoming train to block them, bu the spies manage to get through. Upon seeing that, Arnold cuts down two trees to block them. When it fails, he blasts them with a laser, but it also fails. Finally, Arnold uses an oil slick. When it fails, the oil follows the spies, leading Sam to realize that it isn't oil, but rubber-eating nanobots, and sends the spies crashing to a tree. Sam is unbelievable that Arnold has become a techno-geek.
She gets Clover's hair and scans it to find out that the Cat's Eye emerald has altered her DNA. When scanning it with Mandy's hair, the same results. The spies try to call Jerry about it, but he tells them about a disturbance nearby.
They find some trouble in a building where people are running away after being turned into nerds. It means that Arnold is in that building.
Inside, they find Arnold talking a muscular man that he went too far for bullying him years ago and wants revenge. He uses the ring to remove the man's muscles and transfer it to him. Sam realizes that Arnold is using the ring to get revenge on the people who are mean him, but Clover states that she doesn't do anything bad to him. That is until she states that she turns him down on a few hundred dates.
Arnold sees the spies and they try to fight him. However, with lots of coolness in him, he beats the spies so easily.
After trapping them, he reveals to turn everyone into nerds while he stays being cool. Sam warns him that his coolness wears off because even he turns everyone in the world into nerds, it is just temporary. Arnold then uses the ring to turn Sam and Alex into nerds.
Just then, Dash arrives looking for his ring and thinks the spies must have it after he fall into the bridge. Alex points out that Arnold has the ring. Dash asks him for his ring, but Arnold taunts him that he's gonna be late for accordion lessons.
While Arnold and Dash fight, Sam has freed herself with Alex and Clover. Arnold is about to fight the spies and Dash, but unfortunately, his coolness wears off, forcing him to flee by his blimp. However, the spies catch up while Dash doesn't.
Arnold begins turning everyone into nerds to transfer all of their coolness into him. Just then, the spies arrive, but Arnold gets into the top of the blimp. When the spies try to get him, he easily blows them away. Just then, Dash arrives and fights with Arnold for the ring. Clover has managed to use a device to destroy the ring, turning everyone back to normal.
Afterwards, Dash is shown being arrested and Arnold asks the spies if they still think he's a nerd. Clover reassures him that he's just coolness-challenged.
At Beverly Hills High School, Arnold has lost being president, but is encouraged about planning to be the spies' mascot.