The Turtles are reviewing a videotape of them rounding up the remainders of Megavolt's ninjas utilizing Donatello's new TurtleCam when they notice someone lurking within the shadows on the tapes. Raphael announces that he has seen that same face at the sight of their last two or three missions. The Turtles are curious as to why someone would be following them and decide to hit the streets to find this mysterious watcher. Meanwhile, from in outerspace, an alien warlord named Dregg (who is introduced in this episode as the Turtles new arch-enemy and Shredder and Krang's replacement) sends his army, called the TechnoGang, to Earth. The alien mob is led by Dregg's second-in-command, HiTech. The gangsters plan to loot the Earth of all it's gold. Apparently gold is the element necessary for Dregg's "master plan".
So while the Turtles are still cruising the streets, the TechnoGangsters' spacecraft enters the Earth's atmosphere with laser guns blasting at the Federal Reserve Building.
The Turtles quickly leap into action, but soon find themselves in a pickle. Suddenly the mysterious watcher arrives on his motorcycle and helps to turn the tide. Unfortunately, he ultimately ends up being more of a hindrance then a help, as the TechnoGangsters escape. But before they can learn his identity - he has escaped as well.
Back at the lair, the TMNT have another problem to contend with as Donatello informs them that the mutagen is proving to be unstable and he has no idea what it effect it may ultimately have on them.
But before he can list some of the errant possibilities, the Intruder Alarm sounds and they rush off into the sewers - only to discover the mysterious watcher lurking about.
After deflecting some impressive martial arts moves, the Turtles learn that the watcher is a teenage boy named Carter and he is seeking the famous sensei, Hamato Yoshi, so that he can learn the technique of the Foot Clan.
Much to the Turtles surprise, Splinter agrees to take Carter on as a student, but only if Carter agrees to follow the "Code of Ninja Honor" - no matter how difficult it may be.
Back on board Dregg's ship, the DREGGNAUGHT, Dregg takes his recent failure in stride and revises his master plan. This time he intends to use the "Earthlings own primitive technology" against them.
Meanwhile at the Copcore Building, April is witnessing the unveiling of the future of law enforcement - THE INTIMADATORS --- robotic cops, designed to detect criminal intent. But Dregg reprograms them and they are out for blood.
April contacts the Turtles who leave Carter behind with strict instructions NOT to touch anything in Donatello's lab—especially the unstable mutagen! The TMNT then rush across town to the CopCor Building.
While wearing Donatello's TurtleCam, Michelangelo broadcasts the images back to their lair, where Carter is able to see first hand the Turtles in action—from their POV.
But after a serious butt-kicking from the Intimidators, the screen goes black. Fearing the worst, Carter decides that the Turtles need his help. As he rushes out of Donatello's lab, he inadvertently, and unknowingly, spills some of the unstable mutagen onto his hand. But at the CopCor Building, once again, Carter's efforts seem to cause more trouble for the Turtles than relieve them. And to make matters worse, Dregg has finally arrived on Earth via his gigantic floating platform in his bid to conquer Earth.
Another battle ensues with Dregg, Hi-Tech and other assorted TechnoGangsters joining the fray between the Turtles and the Intimidators.
But Hi-Tech and the TechnoGangsters had not counted on the tenacity of the Turtles and are finding it difficult to defeat them.
Dregg decides that to make the Turtles tow the line, he needs a hostage... and Carter is just what the doctor ordered.
So while Dregg returns to the Federal Reserve Building to finish stealing the gold, Carter is locked in a sealed metal hold and clamped into a mechanical claw. The kid is angry at himself for not being effective in his efforts to help the Turtles, and then he suddenly mutates (thanks to the spill back in Donatello's lab) into a giant bio-mechanical, yellow, mohawked, metallic-skinned ninja.
Meanwhile, the Turtles have destroyed one Intimidator and Donatello has reprogrammed the other to help them defeat Dregg and his TechnoGangsters.
Back at the Federal Reserve Building, the Turtles destroy Dregg's Flying Platform and with the help of the Metal-Mutant Carter, defeat Dregg, causing him to return to his Dreggnaught claiming to seek revenge.
Unfortunately, the Turtles believe that Carter perished during the fire fight and are relieved when he shows up at the lair the next day. Now all they have to do is figure out who was the "mystery mutant" that saved them.
- Leonardo (Cam Clarke)
- Donatello (Barry Gordon)
- Michelangelo (Townsend Coleman)
- Raphael (Rob Paulsen)
- Splinter (Peter Renaday)
- April O'Neil(Renae Jacobs)
- Carter (Bumper Robinson)
- Lord Dregg (Tony Jay)
- HiTech (Rob Paulsen)
- Copcor President (Peter Renaday)
- Copcor Scientist (???)
- Turtles' Lair
- Turtle Blimp
- Carter's Motorcycle
- Dregg's Ship
Home media releases
- Teenage Mutant Ninja Turtles Season 9
- Teenage Mutant Ninja Turtles: The Complete Classic Series Collection
- When Carter saves the turtles from Lord Dregg's robots, Leonardo says "Thanks for the assist, Carter." As he says this, he is in front of Carter. But in the next shot, he's behind him.
- This episode marks the first appearances of Lord Dregg, Carter, Hi-Tech, the Technogangsters and the Dreggnaught. Though not given away in this episode, Dregg has particularly been introduced as the Turtles new main villain and the replacement for Shredder and Krang, who were banished to Dimension X for good in the previous episode "Turtle Trek".
- Also from this episode on, April no longer works for Channel 6 (which no longer appears), and has now become an independent reporter. The reason why she left Channel 6 is never revealed in the remainder of the show.
- One of the people April is with looks like an animated version of Professor Jordan Perry from Teenage Mutant Ninja Turtles II: The Secret of the Ooze.
- This episode and all episodes of Season 9 are the only season that Shredder and Krang do not make a single appearance at all, yet strangely, the opening and theme song still portray Shredder as the main villain.
- April and the turles are now animated differently for the first time which will remain that way for the rest of the series' run. They now have a more cartoon-ish appearance and April has a new bobbed hairstyle. Oddly however, the opening still uses clips from the previous season and its animation style.