TV newswoman Lee Carter witnesses the assassination of presidential candidate Charles Carroll atop Seattle’s Space Needle. A waiter armed with a revolver is pursued and falls to his death while a second waiter, also armed, leaves the scene unnoticed. A congressional committee decides the killing was the work of the dead waiter but conspiracy theories subsequently arise. Three years later, Carter visits her former boyfriend, newspaper reporter Joe Frady, claiming others must have been behind the assassination as six of the witnesses to the killing have since died and she fears she will be next. Frady does not take her seriously. Carter is soon found dead in what is officially ruled as a massive drug overdose coupled with a DUI.
Guilty over disregarding Carter’s pleas for her safety, Frady goes to the small town of Salmontail to probe the recent death of Judge Arthur Bridges, also a witness. An apparently spontaneous bar fight with the Salmontail sheriff’s deputy draws the attention of the sheriff himself, L. D. Wicker, who offers to take Frady to the spot where Bridges drowned. When they arrive at the dam, however, Wicker pulls his gun on Frady while the floodgates are opening, plotting to have him drown the same way Bridges did. Frady whips Wicker with his fishing rod, and they tussle in the rapids. Frady manages to make it to the rocks of the river bank, while Wicker drowns. Frady commandeers Wicker’s squad car, and at the sheriff’s house he uncovers documents about the Parallax Corporation. The documents reveal the organization recruits political assassins.
While Frady collects the documents, the deputy arrives at the residence, letting himself in. Frady grabs the documents and attempts to escape in Wicker’s squad car, with the deputy in pursuit. Frady smashes the squad car through the front of a grocery store, and escapes through the back, jumping into the back of a passing commercial vehicle.
Frady tries to convince his skeptical newspaper editor Bill Rintels he is onto a big story, connecting the dots of witnesses of assassinations who have died, but Rintels refuses to support his efforts. Undaunted, Frady seeks out a local psychology professor, Dr. Schwartzkopf, who assesses the Parallax Corporation’s personality test taken from Wicker’s desk, and deems it to be likely a profiling exam to identify psychopaths.
Austin Tucker, the paranoid aide to the assassinated Carroll, agrees to meet Frady on his boat, while anxiously revealing there have been two attempts on his life since Carroll’s assassination. Shortly after Tucker shows photos to Frady of a suspicious waiter who may have been involved in Carroll’s shooting, a bomb explodes onboard, killing Tucker and his assistant. Frady survives by diving overboard but is believed to be dead.
Later that night, Frady slips into the newspaper’s offices, startling a sleeping Rintels, revealing he’s alive despite reports that he died in the boat accident. Moreover, he informs Rintels of his belief he’s uncovered an organization that recruits assassins, and wants the public to believe he is dead so he can apply to the Parallax Corporation under an assumed identity.
Days later, Jack Younger, a Parallax official, pays him a visit to let him know he is, based on his preliminary application, the kind of man Parallax is interested in. Younger is encouraged by Frady’s aggressive act of throwing a pot that has burned his hand against the wall. Frady is accepted for training in the Parallax Corporation’s division of Human Engineering in Los Angeles, where he is instructed to watch a slide show conflating positive images with negative actions.
While leaving the Parallax’s offices, Frady recognizes one of the Parallax operatives from a photo Tucker showed him, as the second waiter from Carroll’s assassination. He watches the assassin retrieve a case from a car, drive to an airport, and check it as stowed baggage on a passenger jet. Frady boards the plane and notices a senator aboard, but cannot find the assassin, who is actually watching the jet’s takeoff from the airport’s roof. Frady writes a warning, that there is a bomb on board, on a napkin and slips it onto the drink service cart. The warning is found and the jet returns to Los Angeles. Passengers are evacuated moments before the bomb explodes.
Returning to his apartment, Frady is confronted by Younger about not being the man whose identity he has been using. Frady ‘confesses’ he is actually yet another man who had gotten in trouble with the police, and Younger agrees to validate this new identity. Later, at the newspaper office, Rintels listens to a secretly recorded tape of the conversation between Frady and Younger, then places it in an envelope with other such tapes. Rintels is poisoned by the senator’s killer and bomb-planter, now disguised as a sandwich delivery man, and the tapes disappear.
Frady goes to the Parallax offices to see Younger, and is told he is not there, but then sees him leaving the building. He follows the operative to the dress rehearsal for a political rally for Senator George Hammond and hides in the auditorium’s catwalks to observe Parallax agents, who are posing as security personnel. Frady attempts to follow one of the men back to the auditorium, but finds he had been locked in the catwalk area. As Hammond drives a golf cart across the auditorium floor, an unseen sniper shoots him in the back, killing him, causing pandemonium below.
Frady realizes too late he has been set up as a scapegoat and attempts to flee across the catwalks, but is spotted by the police who are now in the auditorium below. As Frady runs to the reopened exit door from the catwalks, a shadowy agent steps through, killing Frady with a shotgun. Six months later, the same shadowy committee that investigated Carroll’s death reports that Frady, acting alone, killed Hammond out of paranoia and misguided patriotism and expresses the hope that the verdict will end conspiracy theories about political assassinations.