Back in England, the Turtles are listening to a historical lecture which Michelangelo finds too tedious to continue. To escape, he launches himself out of the castle in a catapult.
While the Turtles enjoy pizza, April leaves for Oxford to tape an interview with a famed historian. Splinter chides Michelangelo for his lack of interest in history, pointing out that seeds of tomorrow's events are the results of the past. They turn on the TV and hear a news report about the invention of an advanced atomic clock, which piques Donatello's interest.
That night, they sneak into the lab where it's kept, but as Donatello touches it, the device suddenly generates a whirlwind that deposits them in a strange, opulent observatory. A man snatches the atomic clock from Donatello and runs away with it, but not before revealing himself to be Professor Moriarty.
As the Turtles chase Moriarty, Sherlock Holmes and Doctor Watson also arrive and literally run into Donatello. The Turtles realize that they've traveled a century back in time, and Leonardo is thrilled to meet the real Sherlock Holmes in the flesh.
The legendary detective takes them back to Baker Street, only to be interrupted by Inspector Lestrade, who brings news of Moriarty stealing scientific equipment from all over Europe. Just then, one of Moriarty's goons shoots a bust of Holmes in front of the window.
The Turtles take a train to Oxford, where Leonardo uses his own deductive skills to track the would-be assassin down into the sewers. They soon find Moriarty's hideout, but he refuses to give back the atomic clock, which is a central part of a time machine he is building.
The Turtles find themselves in the present once again, but are horrified to find that armed troops are parading through the streets with the "emperor of the world," Moriarty. They're chased by his armed goons and end up in the river, then encounter an alternate version of April, who is working alongside alternate versions of Burne and Vernon to thwart Moriarty. Fortunately they know where the time machine is, and are able to take the Turtles there. April also gives a hungry Michelangelo an apple to eat.
Unfortunately, Moriarty has predicted their plan and is waiting for them. Donatello manages to grab the atomic clock in the ensuing fight, and another time-whirlwind is triggered that deposits them back in their own timeline. Moriarty is also there and tries to steal the atomic clock again, but the Turtles are able to stop him, only for him to vanish back into the past. Michelangelo tosses the atomic clock to the night watchman as the Turtles flee the building.
The Turtles return to the London sewers, where Splinter and April are waiting for them. Much to April's surprise, her bag holds an apple core.
- Leonardo (Cam Clarke)
- Donatello (Barry Gordon)
- Michaelangelo (Townsend Coleman)
- Raphael (Hal Rayle)
- Splinter (Peter Renaday)
- April O'Neil (Renae Jacobs)
- Vernon Fenwick (Peter Renaday)
- Burne Thompson (Pat Fraley)
- Sherlock Holmes (Peter Renaday)
- Dr. Watson (Pat Fraley)
- Professor James Moriarty (Hal Rayle)
- Moriarty's Trooper (Barry Gordon)
- Pizza Delivery Guy (Cam Clarke)
- 20th Century/Victorian Night Watchman (Pat Fraley)
- Newsreader (Peter Renaday)
- Inspector Lestrade (Hal Rayle)
- Air Gun Cane Goon (Cam Clarke)
- Turtles' London Lair
- Greenwich Observatory
- 221B Baker Street
- Streets of Oxford
- Imperial Science Museum
- Moriaty's coach
- Sherlock Holmes' coach
Home media releases
- Teenage Mutant Ninja Turtles Season 7
- Teenage Mutant Ninja Turtles: The Complete Classic Series Collection
- As the Turtles were entering the Imperial Science Museum from the underground tunnel, Leonardo had Raphael's colors. He later had Raphael's colors when first dueling Moriarty with his katana.
- When the 19th century nightwatchman said that the observatory wasn't open to turtles, a shot of the Turtle's London sewer lair wall was seen behind him.
- When finding the secret entrance to Moriarty's hideout, Raphael was seen with Leonardo's colors.
- When the Victorian policeman entered the observatory it was daytime outside even though the atomic clock theft happened at nighttime.
- When Holmes' bust landed near Michelangelo on the floor, his nunchuks were upside down.
- Holmes' bust was missing from the window when Watson took cover.
- When the turtles stand up after taking cover, Michelangelo has Donatello's colous.
- When Donatello drew his bo to duel Holmes, it showed the background of the Turtles exiting the sewers into Moriarty's alternate 1991 instead of the flight of steps that led to the observatory.
- When Leonardo examines the soot trail, the spectacles the turtles were wearing as part of their disguises have disappeared for a brief shot. They then disappear completely once they enter the sewers.
- When Leonardo shouts "Down that alleyway!" after the air gun cane smashed the tea room window, he and Donatello's colors were switched.
- The turtles lose their hats after jumping into the river. But after they meet up with April and she goes to open the secret book case passage they have their hats again.
- When Raphael says "Nice save, Leonardo" after returning to their own time, his mouth doesn't move.
- When the Turtles were traveling to Oxford via train, the coal on the coal wagon is colored green.
- When the train stops at Oxford station, there is a woman on it wearing modern dress even though it's set in the 19th century.
- This is the final episode of the "Vacation in Europe" sideseason.
- Holmes: Not bad for a turtle!
- Donatello: Not bad for a skinny Englishman!