George Nada, portrayed by Roddy Piper, is a down-and-out laborer who arrives in Los Angeles in search of employment. The city is rife with economic hardship, leaving many, including Nada, to struggle in shantytowns. After listening briefly to a street preacher (Raymond St. Jacques), he dismisses the man's warnings and flees from impending police trouble.
Nada eventually secures a job at a construction site, where he meets Frank Armitage, a fellow worker who grows suspicious of Nada's intentions. However, after confronting Nada, Frank offers him refuge in the nearby shantytown after realizing Nada only seeks companionship and a meal. Their hospitality is interrupted when Nada witnesses strange occurrences at a nearby church, where police helicopters seem to surveil a congregation engaging in peculiar behaviors. As he investigates, Nada discovers that the church acts as a front for a more sinister operation, hiding scientific apparatus and boxes containing mysterious sunglasses.
The night turns chaotic as police arrive, devastating both the church and the shantytown. The following day, Nada returns, seeking answers; he finds and opens one of the boxes, revealing the cheap sunglasses. Curiosity leads him to wear a pair, causing his world to transform into a bleak reality where subliminal messages plastered on billboards command the masses to “OBEY” and “CONSUME.” Each unsuspecting passerby is revealed to be a grotesque, alien creature masquerading as humans. Thinking quickly, Nada escapes the absurdity and confronts the aliens disguised as people in a grocery store, leading to an explosive confrontation with law enforcement.
In a moment of defiance, he exclaims, > “I have come here to chew bubblegum and kick ass... and I'm all out of bubblegum.” This declaration ignites a frenetic shootout at a bank teeming with aliens and their collaborators. In a bid to evade capture, Nada escapes to the home of a television executive, Holly Thompson, in hopes of enlisting her help, only to find himself betrayed.
The next morning, Nada frantically seeks Frank for support, but faces skepticism and a brutal confrontation when he attempts to convince him to wear the sunglasses. After a lengthy, intense fight, Frank finally sees the world from Nada's perspective and joins him in resisting the alien invaders.
Together, they uncover a community of rebels who inform them of the aliens' control over Earth's population through a pervasive television signal. With the clock ticking, they learn about a device capable of revealing the sinister truth. Tensions rise as their hideout is besieged by authorities, forcing Nada and Frank to flee once more. Escaping into underground passages, they stumble upon a high-tech alien compound and the source of the overwhelming signal.
A decisive battle ensues at a local TV station, leading Nada and Frank to confront a multitude of alien guards. With their fate hanging in the balance, they make an audacious plan to shut down the signal. However, betrayal lingers as Holly turns against them. In a shocking twist, she eliminates Frank, leaving Nada isolated but resolute.
Realizing he is trapped, Nada uses a hidden weapon to kill Holly, then courageously destroys the broadcast antenna, knowing it could cost him his life. As he is fatally shot, he offers one final act of defiance to his alien oppressors, flipping them off as he succumbs to his injuries. In the aftermath, the truth finally comes to light for humanity, revealing the aliens hiding among them, leaving society forever altered.
