ALLIGATOR

In 1968, a teenage girl purchases a baby American alligator while on vacation with her family at a tourist trap in Florida and gives it the name Ramon. When the family returns home to Chicago, the girl's surly, animal-phobic father promptly flushes it down the toilet and into the city's sewers.

The baby alligator survives by feeding on the discarded carcasses of pet animals (mostly dogs) used in illegal experimentation and dumped into the sewers. These animals had been used as test subjects for an experimental growth formula intended to increase agricultural livestock meat production. However, the project was abandoned because while the formula had the desired effect of making the animals larger than normal, it had the unwanted side effect of massively increasing the animals' metabolism, causing them to develop an insatiable appetite. During the 12 years spanning 1968 and 1980, the baby alligator bioaccumulates concentrated amounts of this formula from feeding on these carcasses, causing it to mutate and grow into a perpetually ravenous 36 foot (11 m) monster with an almost-impenetrable hide.

The alligator begins ambushing and devouring sewer workers. The resulting discovery of body parts exiting the sewers draws in world-weary police detective David Madison who, after a horribly botched case in St. Louis, has gained a reputation for being lethally unlucky for his assigned partners. As David works on the case, his boss Chief Clark introduces him to herpetologist Marisa Kendall. Kendall was in fact the teenager who bought the baby alligator in 1968. The two of them edge into a prickly romantic relationship, and during a visit to Kendall’s house, Madison bonds with her motor-mouthed mother, Madeline.

Madison's reputation as a partner-killer is confirmed when the alligator devours a young officer named Kelly who accompanies Madison into the sewer searching for clues. No one believes Madison’s story due to a lack of a body, and partly because of Slade, the influential local tycoon who sponsored the illegal experiments and therefore wants the truth concealed. This changes when obnoxious tabloid reporter Thomas Kemp, one of the banes of Madison’s existence, goes snooping in the sewers and procures graphic and indisputable photographic evidence of the beast at the involuntary cost of his life. The story quickly garners public attention, and a citywide hunt for the monster is called for.

An attempt by the police to flush out the alligator proves unsuccessful, forcing the alligator to escape from the sewers and come to the surface, where it first kills a police officer and later a young boy who, during a party, is tossed into a swimming pool in which the alligator sought rest. When Madison makes the connection between the alligator and the illegal growth formula experiments, Slade uses his influence with the mayor to get Madison suspended from the force.

The ensuing hunt continues, including the hiring of pompous big-game hunter Colonel Brock to track the animal. Once again, the effort fails: Brock is devoured, and the police trip over each other confusedly. The alligator goes on a rampage through a high-society wedding hosted at Slade's mansion, eating alive a female waiter serving guests at the reception and killing Slade, the mayor, and Slade's chief scientist for the hormone experiments, who was also his intended son-in-law. Madison and Kendall finally lure the reptile back into the sewers before setting off explosives, killing it. As they walk away, a drainpipe into the sewer spits out another baby alligator, thus potentially repeating the cycle all over again.

The alligator is ultimately destroyed when police detective David Madison lures it into an explosive trap and detonates a time bomb, killing the creature beneath the city.

The film concludes with the monstrous alligator’s reign of terror coming to an explosive end, symbolizing both the dangers of unchecked scientific experimentation and the persistence of urban legends. By having the protagonist use ingenuity and courage to defeat the beast, the film delivers a cathartic resolution while maintaining its satirical edge about city corruption and reckless science.