The film opens with a late-shift worker in the basement floor of a textile company feeds bales of cotton into a large industrial machine. He takes a break and notices the thermometer on the wall indicates the temperature is over 100 degrees. In anger at the heat, the worker pounds his fist against a support beam and a rusty nail protruding from the beams punctures his hand. He goes to the medical cabinet and gets an anti-bacterial ointment and gauze for his wound. As rats accumulate to watch the late-shift worker, he starts to taunt them and threaten them. He tosses a rat into the large industrial machine and we watch the rat being torn to pieces and blood staining the cotton. As he continues the taunts, the rats watch on. A large shadow appears and the worker turns to a sight that scares him. He stumbles backwards into the industrial machine and is slaughtered. His remains are eaten by the rats.The next day, an exterminator (Brad Dourif) crawling onto the roof of an industrial building dragging a fire hose. He stuffs the end of the water hose down into the ventilation pipe of some indoor plumbing. Behind the building is a stream of running water. A man in the water is waiting by a pump motor for the exterminator to finish preparing the hoses. The exterminator indicates to the partner on the ground that he is ready to begin. The partner cranks the pump motor and begins pumping water into the building while sucking out water through hoses in the basement of the building, bringing with it many rats, and emptying the rats into the stream.A drifter named John Hall (David Andrews) comes into a small town looking for work. The local textile company is the largest employer in town, so he applies there. The foreman, Warwick (Stephen Macht) agrees to hire the drifter after first harassing him over being a drifter and having college experience listed on his application on the condition that John accepts minimum wage for the first 4 weeks and works the 11pm to 7am "Graveyard Shift".Warwick meets with a building inspector who threatens to condemn the building if the rat infestation isn't cleared up and the basement cleared of the massive amounts of old materials stored. Warwick pays-off the inspector $200 cash to give him some time to get the building in order before filing his report. The inspector takes the money and gives Warwick until after the 4th of July holiday weekend to clean up the building.As Warwick sends random employees down to string lights in the basement, prior to the cleaning detail, one by one they get attacked and killed by some unknown creature that lurks in the basement. Always, a tide of rats preludes the attacks. When the employees come up missing, the "Now Hiring" sign gets posted out front, but no more mention of the incident occurs.Warwick explains to some workers that the business will be shut down for the 4th of July holiday. Those workers that belong to the Union would be paid holiday pay. Those who were not Union would be laid-off for one week, unless they agreed to be part of the clean-up detail and receive double-pay for their efforts. Six workers are chosen for the clean-up detail work. John Hall is one of them.One night, John Hall finds a trap door leading down further under the building. The group of six cleaners and Warwick head down to investigate. After the stairs leading back up collapse and the seven people realize they are trapped with a monster they begin to turn on each other, trying to escape. One by one, the monster kills the group off until John Hall and Warwick remain. Warwick is consumed with trying to conceal this event and also punish John Hall for standing up to his bullying, so he tries to kill John. Warwick confronts the monster and dies during the ensuing fight. John scrambles back up to the basement of the building where the large industrial machine is. The monster attacks him there, where we see that the monster is a very large bat. The large bat gets its tail caught in the industrial machine and John turns it on. We watch the bat being dragged into and slaughtered by the machine.John sighs relief.The last scene shows that the textile mill is now "under new management."Credits roll.
Output: Question: What does the workers find?, Answer: A subterranean maze of tunnels