The Bachman Textile Mills in Gates Falls, Maine, has a severe vermin problem. Recently re-opened for business, its filth-clogged floors are a breeding ground for nests of hungry rats, who have developed a taste for human meat from frequent snacking at the graveyard next door, while a succession of gruesome accidents have got the place a bad reputation. Enter John Hall (Andrews), a college-educated drifter whose quiet cool puts up the backs of his proletarian thug fellow workers and of the maniacal foreman Warwick (Macht), and, after a few showy rants, exit Vietnam vet exterminator Brad Dourif, given special billing for a few memorable speeches ("I'm not one of those baby-burnin', flashbackin' fuck-ups you see Bruce Dern playing"), and squashed by a gravestone before the plot really gets going.
Warwick puts everyone he doesn't like on the basement clean-up crew over a holiday weekend, and they all venture into the forgotten cellars of the mill, where lurks a monster that resembles a giant rat-tailed fruitbat. Such B-movie favourite characters as the Fat Creep Who Gets What He Deserves, the Black Dude Who Ill-Advisedly Puts His Arm Into A Whole And Has It Chewed Off, the Stupid Woman Who Twists Her Ankle At The Worst Possible Moment and the Gutless Cretin Who Goes Hysterical become monster munchies, while the two main characters struggle with the lamest possible horror movie plotting and a fairly laughable bit of neo-Marxist message-making, in which the factory is seen as an extension of the monster, grinding up working men for money.