Sometime after the events in ''Critters 2: The Main Course'', Charlie MacFadden is tracking down the last of the Critters. A family of three – Annie (the main protagonist), Johnny (her little brother) and Clifford (the father) – stops at a rest stop when their car's tire pops. At the rest stop, Charlie warns them and Josh, stepson of a corrupt landlord, about the Critters. As this happens, a Critter lays eggs under the family's car and the family leaves, unknowingly taking the eggs with them. Soon after they arrive at their tenement, the Critters hatch and attack the sleazy maintenance man, Frank. When the landlord arrives, he too is eaten by the Critters after Josh locks him in Clifford's room, unknowingly trapping his stepfather with the creatures. Next, one of the residents is attacked and wounded. Annie, her family and five others (including Josh) try to get to safety in one piece by getting to the roof of the building. Charlie arrives and destroys the remaining Critters, saving the remaining tenants. The film ends in a cliffhanger as Charlie is about to destroy two Critter eggs, but is ordered not to and a containment pod sent from the Intergalactic Council crashes into the basement.