Some TMNT stuff really isn't for little kids.
Eric Sacks was born on an American military base in Japan. His father went to fight in the Vietnam War and was killed, and Sacks grew up as an outsider. He was adopted by a "sensei" and instilled with a love of Japanese culture and honor. He was particularly enthralled by a story in which an evil warlord who had poisoned the town's water supply was defeated thanks to a powerful alchemist.
Sacks moved to New York City at some point, becoming a wealthy businessman and scientist. There, he worked alongside a scientist by the name of O'Neil in creating a "Mutagen", which he had intended to use as an antidote to a chemical attack he and his Master Shredder would unleash on New York. Sacks wished to use the antidote to pretend to be a hero and reap financial rewards. The Mutagen was tested on a rat and four Turtles, but when O'Neil uncovered Sacks' true plan, he torched the lab to destroy the research. O'Neil's young daughter rescued the test subjects and let them loose near a sewer grate, but the doctor himself was killed by Sacks.
For fifteen years, Sacks attempted to recreate the Mutagen, but it proved difficult without the project's notes and one of its chief scientists. In the meantime, Sacks and Shredder had started the Foot Clan, a paramilitary organization, to steal components for the Mutagen and generally spread fear throughout New York City. Dr. O'Neil's daughter April, now a lifestyle reporter for Channel 6, attempting to break through to a higher position, begins chasing leads on the Foot. She ends up encountering the four Turtles, now mutated into anthropomorphs. Remembering Sacks as her father's kindly boss and seeing his open philanthropy and will to extinguish the Foot Clan, she opens up to him about the Turtles, alerting him of their survival. He begins to formulate a plan with Shredder to capture the Turtles and extract the Mutagen from their blood.
The Turtles take April to meet their father, the former lab rat Splinter, and the Foot Clan track down the Turtles into their Sewer lair. Shredder and a great many Foot Soldiers attack them, and bring back three of the Turtles for extraction - leaving Raphael behind, as one Foot Soldier had reported him dead.
Splinter, who was badly wounded in the fight with Shredder, urges Raphael and April to rescue the other Turtles. Together with April's ex-coworker Vern, Raph and April storm Sacks' upstate compound as he is finishing the Mutagen extraction. While Raphael is distracted with fighting Shredder, he takes a helicopter back to his tower in the heart of New York City.
While Shredder works on dispersing the gas and the Turtles attempt to stop him, Vern and April make a move to collect the Mutagen. They find Sacks there, and he fends them off with a gun, also revealing that he killed April's father. He lightly wounds Vern, and April sets off the sprinklers. Vern grabs a microscope and clocks Sacks on the head, knocking him out.
- In earlier marketing materials and promotions, Sacks was distinctly said to be The Shredder. In the final product of the film, however, they are two separate characters. However, in the Nintendo 3DS game based on the film, Sacks still is Shredder.
- Many marketing and promotional materials spells his surname as "Sachs", but it is distinctively given as "Sacks" in officially released media in which he appears.