Leonardo, Michelangelo and Raphael are preparing to watch a cheesy sci-fi movie when Leonardo wonders where Donatello is, and becomes concerned that he is spending too much time on scientific endeavors. But when they ask him to join them, he anxiously says that the Earth's orbit is moving the planet closer to the Sun. He becomes even more agitated when he sees that the movie they are forcing him to watch is The Day the Earth Collided with the Sun.
At Channel 6, Vernon is irritating his coworkers with news of Foster Fenwick, his genius nephew. Foster arrives with two heavy suitcases of scientific equipment, since he has an exhibit at the Junior High School Science Fair.
The other three turtles ask Splinter what they should do about the increasingly overwrought Donatello. Splinter arranges a practice match involving all four Turtles, but a distracted Donatello successfully beats the other three before wandering off to do more scientific research.
Since Foster wants to meet the Turtles - especially Donatello - Vernon appeals to April for help. The other Turtles convince the reluctant Donatello to come meet the arrogant little boy, only to discover that Foster's scientific achievement is a solar magnet that is drawing the Earth closer to the sun. Donatello goes berserk and starts tearing the solar magnet apart before the other three can drag him out of the room. On the way home, they berate him for what he did even as the temperature keeps going up.
Unbeknownst to them, Professor Filo Sopho steals the solar magnet. Its theft is discovered when Foster is being interviewed on live TV, and he - as well as Raphael and Michelangelo - assume that Donatello was the thief. However, Professor Sopho hijacks the airwaves and declares that he has the solar magnet, and is pulling the Earth towards the sun in order to kill everyone on the surface.
Foster demands to come with them, on the basis that only he can dismantle the solar magnet. Much to Donatello's dismay, he declares coming along only to meet his idol, Professor Sopho.
The heat grows more intense, melting the tar on the road and popping corn in the fields. The Turtles, Vernon and Foster make it to Sopho University but find it abandoned, though some fresh footprints and a muddy shovel help them figure out where Sopho's new hideout is. They arrive at a park just as the trees start bursting into flame, and head down into the sewers beneath it.
Unfortunately Sopho has a forcefield net to keep them from getting to him. Foster crawls through and introduces himself to Sopho, until the scientist orders his goons to get "this brat" out of the place. Foster manages to overwhelm his captors and switch off the forcefield, allowing the Turtles to defeat Sopho and his two goons.
Foster and Donatello figure out a way to blow up the solar magnet, which will stop the Earth from being destroyed. Sopho rages at Foster that no true scientist would destroy his own invention, to which Foster retorts that no true scientist would try to destroy the world. That evening, the Turtles enjoy pizza with Foster, who dedicates a toast to Donatello.
- Leonardo (Cam Clarke)
- Donatello (Barry Gordon)
- Michelangelo (Townsend Coleman)
- Raphael (Rob Paulsen)
- Splinter (Peter Renaday)
- April O'Neil (Renae Jacobs)
- Burne Thompson (Pat Fraley)
- Vernon Fenwick (Peter Renaday)
- Foster Fenwick (Dana Hill)
- Professor Filo Sopho (Rob Paulsen)
- First Goon (Barry Gordon)
- Second Goon (???)
- Solar Magnet
- Soil tracker
Home media releases
- Teenage Mutant Ninja Turtles Season 6
- Teenage Mutant Ninja Turtles: The Complete Classic Series Collection
- Leonardo has Donatello's colours when he shouts at Donatello who he tears apart Foster's solar magnet.
- In a shot shortly after said color switch, Raphael's teeth are red as he grimaces.
- Sopho's goons' hand blasters switch hands during the fight against the Turtles.
- The sofa the Turtles sit on in front of the TV has four seats, but usually has three.
- Raphael mentions the events of Donatello's Degree: Michelangelo breaks the fourth wall by exclaiming "I think I missed that episode."
- Second and final appearance of Professor Sopho.
- First and only appearance of Foster Fenwick.