Roy Knable (John Ritter), a couch potato, is a struggling Seattle plumbing salesman and former fencing athlete who spends most of his spare time watching hours of television. Roy's neglected wife Helen (Pam Dawber), a senior vitamin product manager, resents the fact that they never do anything special or romantic together anymore.
After a fight (which involved Helen smashing the family television screen with one of Roy's fencing trophies as a wake-up call to reality), a shady man named Mr. Spike (Jeffrey Jones) appears at the couples' door, offering him a new high tech satellite dish system filled with 666 channels of programs one cannot view on the four big networks (CBS, NBC, ABC, and Fox). What Roy doesn't know is that Spike (later referred to as "Mephistopheles of the Cathode Ray") is an emissary from hell who wants to boost the influx of souls by arranging for TV junkies to be killed in the most gruesome and ironic situations imaginable. The 'candidates' are sucked into a hellish television world, called Hell Vision, and put through a gauntlet where they must survive a number of satirical versions of sitcoms and movies. If they can survive for 24 hours they are free to go but if they get killed then their souls will become the property of Satan (the latter usually happens).
The dish eventually sucks Roy and Helen into this warped world. Roy and Helen first appear on a bizzare game show called 'You Can't Win' where they are forced by the game show host to answer personal questions about their failing marriage or be "eliminated". They succeed and as their prize are pushed through a porthole into another world called 'Underworld Wrestling Foundation' and are forced to wrestle a stout couple called The Gorgons. When Roy is bested, Helen defeats Mr. and Mrs. Gorgon by bashing them with a microphone stand and for their reward, are pushed into another porthole to another channel.
Watching the Knables from the confines of HTV's control room is Spike, who is soon joined by Crowley (Eugene Levy), a nerdish employee who brings along Pierce (Erik King), a younger upstart employee to the TV center. Crowley explains the events happening to Pierce. They watch another couple, the Seidenbaums, on another channel where the shrewdish wife is crushed to death by a Godzilla monster while her henpecked husband escapes. After Crowley makes a sly comment to Spike about a previous individual who survived the 24 hours in HTV's dimension. Spike bannishes Crowley to the Hell TV world by zapping him with a special remote control device he always keeps on him.
Back in the real world, Roy and Helen's 11-year-old son Darryl (David Tom), and his older sister Diane (Heather McComb) arrive home from school and are puzzled to their parents absence. They find the large HTV set in the living room as well as the large sattelite dish in their back yard. While Diane invites some of her school friends over, Darryl watches the new TV set and is behildered by the various HTV programming which includes hellish spoof shows like "Cruel Practical Jokes", "Three Men and Rosemary's Baby", "thirtysomething-to-life", etc. When Darryl goes into the backyard, the motion sensitive dish activates and tries to suck him into the Hell TV world, but zapps his bicycle instead. When Darryl sees his bicycle on the TV later in a show called "Meet the Mansons" he tries to convince Diane that something sinister is going on, but she dimisses his theories.
Meanwhile, Roy and Helen are trapped in a sub-freezing snowy forrest area on the HTV show "Northern Overexposure" where they venture to a frozen lake and meet Crowley who is digging holes in the ice to find a conduit to the next channel. Just when Crowley finds a dimentional opening, they are attacked by savage wolves and forced to take shelter in a nearby shack where Crowley explains to them about their situation and that they have 15 hours left to survive HTV's world. In attempting to escape from the shack, Crowley is overwhelmed by the wolves and the shack is set on fire from a dropped oil lamp.
Roy and Helen are forced to leave Crowley behind and jump through the dimentional porthole and find themselves as animated mouse characters in a cartoon and are forced to battle a mechanical robot cat that chases them. Darryl sees his parents as animated characters and watches their actions on the screen. Helen travels through a mousehole into another channel, but Roy is left behind to deal with the robot cat, which he defeats by sending for a mechanical robot dog. Roy then runs through the conduit to find Helen and ends up on a Saturday Night Live theme show called 'Saturday Night Dead' on a segment called "Duane's Underworld" as a captive guest. Roy manages to escape and finds himself in a black-and-white channel as a private detective in his search for Helen.
In the meantime, Darryl finally convinces Diane where their missing parents are by showing them on the TV set and they try to help them survive any way possible. Roy finds Helen being held by Mr. Seidenbaum, their former next door neighbor, who has set himself up in this cloak-and-dagger show as a nightclub owner. When a gangster arrives and begins shooting up the place, Seidenbaum is fataly hit and as his final act, gives Roy and Helen his remote control device that he has somehow smuggled into the HTV world. Roy and Helen use it to escape but they loose the remote control after they find themselves in the next channel on a period piece show called "Off With His Head" set in 18th Century France where Roy and Helen are aristrocrats being chased by Parisian citizens during the French Revolution. They are reunited with Crowley, who has survived he wolf attacks despite the loss of his right leg and arm, who tries to help them escape, but they are soon captured by French soldiers and taken to a town square to be executed.
Darryl and Diane try to help by hacking into the TV set's cable database to access the system just as the countdown to Roy and Helen's time is to expire. They manage to prevent Roy from being beheaded long enough for the clock to expire and Roy and Helen are saved by the clock to announce the end of their 24 hour trial period in HTV.
This infuriates Spike to the point that he makes good on Roy's contract, releasing him but not Helen as she was not in the system under contract. Spike then transports himself into the HTV world and spirits Helen away to a Western site where he ties her to a cart sitting across a railroad track for her to be run over by an oncoming train in order to lure Roy back into HTV to kill him once and for all. Roy re-enters the HTV system to save Helen, bringing his own remote control with him, allowing him to control their journey. Roy battles Spike in a climatic chase across the HTV system shows from "Star Deathtreck: The Next Generation", to "Driving Over Miss Daisy" to "Underworld Professional Hockey" to a medivial show were Roy's remote control gets destroyed. With assistance from Darryl who throws a fencing sword at the sattalite dish to fight with Spike, they battle across a medivial mansion where Roy tries to get at Spike's remote control device.
Roy confronts Spike in a Salt-N-Pepa music video where after both men chase Spike's remote control around, Roy finally gets a hold of it and bannishes Spike back to the medival world and uses it to save Helen from being run over by a train in the western movie. By pressing the "off" button on the remote, they are evicted from the TV set moments before it sucks their neighbor's abusive Rottweiler into the TV and it destroys itself.
Spike gets eliminated by the Rottweiler in the medivial world while Crowley shows up to watch, and Pierce takes over Spike's place in the HTV control room.
In the final scene, Roy, who has learned a valuable lesson after his adventure, has dramatically cut back on his TV viewing and taken a new job as a fencing teacher.