Some TMNT stuff was always meant for grownups.
Meggan Tully, while dating George Hill, is abducted by aliens and impregnated. The event is removed from her memory and she is returned to her car. George believes the child is his and marries Meggan.
When the unusually shaped child is born, Meggan and George chain her up in the basement, with only a television set for company. They believe the child to be a punishment for their pre-marital sex.
After years of guilt and suffering, George and Meggan Hill commit suicide and Sarah is found by the paper delivery boy. The local police are afraid to enter the basement and call in an officer - called Dragon - from the Chicago Police Department, who releases Horridus and takes her to his station house.
CPD's Captain James Stewart is extremely enthusiastic about assembling a superhuman strike force for his department and recruits Sarah Hill, giving her the codename Horridus, to his "Freak Force" program. There, she meets Dragon, Rapture, Barbaric and Ricochet who at the time is too young to join the department. Due to restrictions imposed by the local government and their police superiors, the 'freak' officers quit the police force and become bounty hunters, allying themselves with the veteran hero Super-patriot and the new Mighty Man.
Freak Force fights a number of menaces, ranging from the super-villains such as the Fantastical Force, the Covenant of the Sword, the Throwaways, Master Atom, Bludgeon, their own evil clones and the Frightening Force, the extraterrestrial Martians, Matrix Swarm and Cosmic Cops, and other heroes like Badrock, the WildC.A.T.S. and Cyberforce.
They even fight their own government; at one point Horridus assists in taking down a secret prison for super types.
Eventually, Horridus and most of her teammates join the United States government's new super-team to replace Youngblood - presumed dead from the Martian attack - the Special Operations Strike force. Horridus gains more worldly and fighting experience.
For a time, Horridus lives with Rapture. However, Horridus still hasn't come to terms with the fact she is very sharp; at one point Horridus destroys Rapture's waterbed, after which Horridus briefly meets the turtles, whom she considers cute. The character had many appearances in the Turtles' own Image comics.
Sara met Michelangelo, and bonded with him over cartoons. She was also affectionate, and the two of them reached third base on a couch. Mikey quickly fell in love with Sara, and their time together inspired him to become a romance novelist. The novel he wrote, "The Rose Among the Thorns", actually managed to become a bestseller and earned the fictional in-universe recommendation of Oprah's Book Club.
However, Sara and Mikey's relationship was always one-sided: Sara had never committed to anything, and Mikey was genuinely surprised (and heartbroken) when Sara gossiped to him about her crush on Officer Dragon and having already moved in with him. Dragon himself didn't even know about this crush, and would later find he felt uncomfortable with it. The relationship Mikey thought he had with Sara turned out to be nothing more than casual sex, as Sara proved to be a vacuous woman with no attention span.
- In Mirage TMNT Volume 4, Mikey had a similar one-sided relationship with another easily-distracted woman, the Styracodon Regenta Seri. The two had sex not long after meeting, and Mikey even fathered children with her, whose eggs she soon laid. But that relationship ended even more bitterly: Seri soon abandoned Mikey to be apprehended by her own guards, and Mikey was locked up without trial in a Styracodon prison.