The Turtles and Splinter are in a museum in London England. The Turtles split up and begin investigating different exhibits by themselves, with Leonardo finding a painting of King Arthur, Queen Guinevere and Excalibur. As the other Turtles marvel at the painting, Donatello scoffs at the idea that Arthur and other such people ever existed.
In Dimension X, Krang is using an element detector to track down a large amount of a rare element, diridium, which could power the Technodrome. It's coming from an ancient tomb, which Krang deduces is the tomb of King Arthur, meaning that the diridium is actually the sword Excalibur.
April and Irma are wandering the streets of London when they encounter the Turtles, who are wearing punk disguises courtesy of Michelangelo. She invites them to a high-society charity event, as long as they find some new disguises.
Upon arriving on Earth, Shredder finds the underground tombs of Arthur and Guinevere, and takes Excalibur for himself, declaring himself "King Shredder the First!" They crash the charity event and start stealing the crown jewels on display, using Excalibur to blast energy at the Turtles when they try to stop him. Leonardo wrecks the tires of his getaway vehicle, forcing Shredder and his mutants to escape on foot.
To stop the Turtles, Shredder brings a pair of stone lions to life with Excalibur, but before the lions can kill the Turtles, an old man suddenly appears and shatters them. Donatello decides that they should research further, and the Turtles come to the conclusion that the old man was Merlin, and that the sword was Excalibur. Just then, Merlin reappears, having been woken from his centuries-long slumber, and horrified to find out that Excalibur has been stolen.
As they set out to find Shredder, the evening news reveals that medieval people are popping up all over London. Donatello concludes that a time shift has been created, and that if they don't restore Excalibur to its rightful place, the world will be consumed in a temporal black hole. To make matters worse, he kidnaps April and Irma so that April can be his queen.
As the Turtles and Merlin catch up to him, they must contend with the vast Black Knights, who obey Shredder's every command. They capture the Turtles quickly, and throw them into the Thames with rocks weighing them down. Leonardo manages to free himself on the prow of a sunken ship, and then frees the others.
Merlin says that they might be able to stop Shredder if they go to Camelot, where he left his book of spells. They head to the ruined castle, which is rebuilding itself as the past and present collide. Unfortunately, Shredder has somehow figured out what they were doing and has the book. Just when all seems lost, King Arthur and Queen Guinevere appear in front of them, and the long-ago king declares that he needs a champion, and the Turtles volunteer.
As part of combat, Donatello is pitted against Bebop, and Michelangelo is pitted against Rocksteady. Both Turtles are defeated, but Shredder refuses to hand over the sword, engaging Leonardo in a sword duel instead. Just when it seems that Shredder has won, Raphael knocks Excalibur from his hand. Shredder begs Krang to rescue him, which the alien brain only agrees to do if Shredder does various chores for him.
Arthur knights the Turtles seconds before the castle falls back into ruin, and Merlin, Arthur and Guinevere all vanish.
- Leonardo (Cam Clarke)
- Donatello (Barry Gordon)
- Raphael (Hal Rayle)
- Michelangelo (Townsend Coleman)
- Splinter (Peter Renaday)
- April O'Neil (Renae Jacobs)
- Irma Langinstein (Jennifer Darling)
- Shredder (Jim Cummings)
- Bebop (Barry Gordon)
- Rocksteady (Cam Clarke)
- Krang (Pat Fraley)
- Merlin (Jim Cummings)
- King Arthur (Hal Rayle)
Home media releases
- Teenage Mutant Ninja Turtles Season 7
- Teenage Mutant Ninja Turtles: The Complete Classic Series Collection
- When the Turtles are first seen wearing their punk disguises, their plastrons are coloured green.
- When April asks Irma if she's admiring London, her belt is colored black.
- When Shredder knights Bebop and Rocksteady with Excalibur, he only places it on Bebop's shoulders.
- When Shredder, Bebop and Rocksteady are in the car, Bebop is sitting in the driver's seat on the left side of the car. In London, England, the driver's seat is on the right side of the car.
- When Shredder unleashes the giant suits of armour at the turtles, we see a shot of Donatello and Leonardo. In the following shot, all four turtles and Merlin are all suddenly standing together.
- During the duel between Donatello and Bebop, Donatello dislodges the log they are standing on, making them both fall into the water. Rather out of character to say the least.
- Donatello's bo strapping is missing when Raphael asks him how to do "this wishing stuff".
- Rocksteady's eyes were coloured white after he, Bebop and the Black Knights pushed the Turtles off the bridges and into the river.