The Lost Son

In an alternate timeline, long before the events of the 2003 series began, Splinter lost one of the turtles to Bishop when he and his men attempted to capture them in the sewers. Believing the youngest turtle had sadly perished, Splinter raised the remaining three but was haunted by nightmares of the one he failed to save.

Sixteen years later, after the Shredder's demise, the family discovers a feral, mutated turtle that has escaped from Bishop's lab and is on the run. They manage to capture this feral turtle, and Splinter strongly believes that he is the lost son of the quartet.

As time passes, the turtles gradually get to know their long-lost brother, named Michelangelo. He, in turn, begins to open up to them as part of the family.

However, with his dark and tortured past haunting him-and with Bishop hot on his trail-the family must protect Mikey from being captured while also managing his feral tendencies. Any sight or reminder of Bishop and his men sends him into a wild rage.

But the real question is this: Is the lost turtle truly the long-lost Michelangelo, or is he merely a dangerous experiment created by Bishop to destroy them?