The Mangler, in Gartley's Blue Ribbon Laundry service, is a laundry press owned by Bill Gartley (Englund). The trouble starts when Gartley's niece, Sherry, cuts herself on a lever connected to the machine and splashes blood on the Mangler's tread while trying to avoid being crushed by an old ice box some movers are clumsily carrying past. Sparks and light streams occur when both the blood and the ice box come into close contact with the Mangler. Later, an elderly worker, struggling to open a bottle of antacids, spills them on the moving tread of the Mangler. When she attempts to collect them, the safety shield inexplicably lifts up and traps her hand inside, followed by her entire body getting pulled into the machine.
Police officer John Hunton (Levine), with the help of his brother-in-law Mark (Daniel Matmor), investigates the incident and the ones that soon follow. As the plot progresses, Mark tries to convince Hunton that the machine may be possessed, and the only way to stop the deaths is to exorcise the machine to dispel whatever demon is inhabiting it.
With the help of Sherry, the two men attempt to exorcise the demon before it strikes again by reciting a prayer and administering holy water. The machine gives one last groan and shuts down. As the three sigh with relief, Hunton takes some antacids, admitting to Mark that they belonged to Frawley. Mark suddenly realizes that the key ingredient in the antacids is deadly nightshade, also called "the Hand of Glory" as outlined in his occult book. Since the machine was accidentally fed the same antacids, Mark realizes that not only was the exorcism rendered useless, as the demon is still alive, it is now stronger than ever. The machine bursts to life and now appears to have a mind of its own, shedding off pieces of metal and rising up in the manner of a wild beast. The three run through the warehouse as they are chased by the now-mobile Mangler.
The Mangler kills Mark while John and Sherry descend a flight of stairs. In their hurry to escape, they fall through a large manhole into the sewer below, the machine struggling to get to them. Suddenly, something falls from the machine into the water, and a mechanical wail ensues. The machine draws back and becomes still, and John and Sherry escape.
Time passes and John goes to check up on Sherry. However, to John's great dismay, he discovers that Sherry has become the new tyrannical owner of the laundry business, going so far as to have the possessed machine rebuilt, resuming its duties.
What is the key ingredient in the antacids?
Nightshade