An unnamed man (Timothy Bottoms) sneaks into Ocean View Amusement Park and places a small radio-controlled bomb on the tracks of the park's wooden roller coaster, The Rocket. The bomb detonates, and The Rocket derails, killing several riders. Safety inspector Harry Calder (George Segal), who initially cleared the ride, is called to the park to investigate. A park worker tells Calder that there was an unauthorized man on the track.
In Pittsburgh the bomber causes a fire at a dark ride at another park. Calder suspects the incidents are linked, and learns that the executives of companies running the largest amusement parks in America are holding a meeting in Chicago. Calder flies to Chicago and intrudes on the meeting. One of the executives plays a tape sent by the bomber, wherein he demands $1 million to stop his bombing campaign.
Back home, Calder is visited by FBI Agent Hoyt (Richard Widmark), who says the extortion money is to be delivered by Calder at Kings Dominion. There, Calder is ordered to wait at a telephone. The bomber calls, warning him there is a bomb in the park. He sends Calder a two-way radio so that he can keep contact, then orders Calder to go on various rides in the park. While Calder is on the Skyway, the bomber tells Calder that the bomb is in the radio. He warns Calder not to throw it away, because it will explode on impact on the crowded paths below. He orders Calder to falsely signal that he has made the delivery, in order to distract the FBI, then leave the money on a bench. Calder complies and walks away. Later, Hoyt admits that he marked the money (violating the bomber's instructions). Calder demands to be sent home and leaves the bomb radio with the bomb squad.
Back home, Calder gets another call from the bomber. He blames Calder for the marked money, and threatens another attack. Assuming it will be directed at Calder personally, he deduces that the next target will be The Great American Revolution at Magic Mountain, a coaster that Calder inspected and cleared. The FBI rejects Calder's hypothesis, but decide to investigate anyway because the ride is scheduled to debut on July 4, when park attendance will be at its highest for the season. Agents disguised as park maintenance men find a bomb attached to the tracks. They safely disconnect the radio antenna.
The bomber returns to his car and gets a new bomb just as the Revolution is about to open. In order to get on board, he pays a park guest $100 for his "Gold Ticket", which entitles the holder to be one of the first passengers. He places the bomb under his seat in the rear of the train. Following the inaugural ride, Calder recognizes the bomber's voice during his ride exit interview with a reporter. He chases the bomber, and alerts the agents that he might have placed something in the train. The train leaves the chain lift on its second ride through.
The cornered bomber threatens to blow up the ride, holding the detonator in his hand while the agents try to jam the signal. He demands a firearm. Calder takes one from an agent and begins to hand it to him. Agents succeed in jamming the detonator's signal, and alert Calder. Calder retains the gun and shoots the bomber, who then runs away. He hops a fence into the field below the Revolution and runs blindly, not realizing he is circling back toward Calder. The bomber climbs onto the track, but sees Calder and freezes. He is hit and killed by the coaster. The ride re-opens following the accident.George Segal as Harry Calder
Richard Widmark as Agent Hoyt
Timothy Bottoms as Young Man
Henry Fonda as Simon Davenport
Harry Guardino as Keefer
Susan Strasberg as Fran
Helen Hunt as Tracy Calder
This was the third film to be presented in Sensurround. Special low-frequency bass speakers were used during the roller coaster sequences. Sensurround was employed in only three other films released by Universal: Earthquake (1974), Midway (1977), and the theatrical version of Battlestar Galactica (1978).
The film features an appearance by the band Sparks for the roller coaster's opening concert, playing the songs "Fill 'Er Up" and "Big Boy" from their 1975 album Big Beat. This appearance was rumored to have been offered to Kiss who turned it down. Sparks later cited their appearance in the film when asked about the biggest regret of their career.
Helen Hunt, in her first feature film role, has the supporting role as Tracy Calder, Harry's teenage daughter and a potential victim of the young man. Steve Guttenberg, also in his first brief film role, plays a messenger at Six Flags Magic Mountain who brings the plans for the Revolution to Calder and Hoyt. Craig Wasson, in his second film, appears as a hippie who sits in the car with the bomber's second bomb at Magic Mountain.
Radio announcer Charlie Tuna also appears in the film as the MC for the concert and the Revolution coaster launch.
Several real amusement parks were used in the film for the various park and roller coaster scenes. Ocean View Park in Norfolk, Virginia was used for the first park in the film. Although the park was located on the Chesapeake Bay, it was described as a west coast park in the film. Goldstone chose the park because of its old fashioned feeling. The park's major wooden roller coaster, The Southern Belle, was renamed "The Rocket" for the film. Kings Dominion in Doswell, Virginia, also appeared in the film. Some of the rides featured in the film, such as the Shenandoah Lumber Company and Rebel Yell wooden roller coaster, still exist today. The final park is Six Flags Magic Mountain in Valencia, California, then just known as "Magic Mountain" (it hadn't yet been purchased by the Six Flags organization). Its Revolution roller coaster was featured prominently in the film's climax.
Originally, Kennywood Park was one of the locations to be used in the film. After the park's owners reviewed the script, they objected. In the end, the park's name was changed to "Wonderworld" and did not appear in the final version of the film.
According to Goldstone, the three parks that appeared in the final film were chosen from over 20 candidates.
Additionally, parts of the movie were filmed at the Hyatt Regency Chicago.
The film's musical score was written by composer Lalo Schifrin.
Despite having been released in the summer of 1977, and being overlooked in favor of the smash hit Star Wars, it went on to be a moderate success at the box office. Reviews were mixed, however. Time Out London felt that 'the results should have been sensational,' but that, 'ultimately the film-makers botched the job. Many of the best runs are interrupted by close-ups, and the filler plot is dumb in the extreme.' Variety said that, 'The rollercoaster rides are the picture’s highlights and they are fabulous.'