In the wake of a devastating nuclear conflict, First Lieutenant Jake Tanner takes on the monumental task of securing the underground missile base of the US Air Force located in the Mojave Desert, working alongside the experienced Major Eugene "Sam" Denton. As they embark on their shift, Denton warns command about Tanner's suitability for their critical mission, leading to a request for a reassignment that heightens the unease in their teamwork. The air is thick with tension as they carry out the necessary security protocols with Sergeant Tom Keegan.
Their routine is abruptly shattered when they detect incoming Soviet nuclear missiles, precipitating a retaliatory strike that results in Tanner and Denton participating in the launch of part of the counter-response. Though US interceptor missiles manage to neutralize approximately 40% of the incoming threats, the nation suffers catastrophic losses, with major cities devastated by the devasting blows.
Fast forward two years, and the Earth is left a shadow of its former self, the axis of the planet dislocated, and grotesque mutations such as giant scorpions emerge due to radiation exposure. The land is ravaged by relentless storms, and an eerie perpetual aurora-like glow casts a haunting remembrance of the apocalypse overhead. Tanner, leaving behind his military duties, now scavenges for supplies in Barstow, California, while Keegan finds comfort in expressing his turmoil through painting in a remnant building of their former base.
As they brace against the mutated scorpions using their high-powered rifles, the harshness of their new survival mode becomes all too clear. Tanner returns from a supply run bearing a stack of Playboy magazines, a seemingly harmless find that soon sets in motion a series of catastrophic events. When an airman, falling asleep with a lit cigarette, sparks a fire, it culminates in a massive explosion that takes the lives of nearly everyone in the base, leaving only Tanner, Keegan, Denton, and Lieutenant Tom Perry alive.
Driven by the hope of finding human connection, Denton feels compelled to trace a mysterious radio transmission that has been broadcasting weekly since the war, setting their sights on Albany, New York. To prepare for this treacherous voyage, the four survivors gear up with two formidable Air Force Landmasters—mighty, 12-wheeled armored carriers armed with rocket launchers, flamethrowers, and cannons, crafted to tackle 60-degree inclines and traverse water. They must navigate the perilous Damnation Alley, deemed "the path of least resistance" amidst dangerously radioactive zones, as they strive to uncover the origins of the enigmatic transmission and salvage the remnants of human civilization.
While traversing the desolate terrain in their Landmasters, one vehicle becomes incapacitated during a violent storm that tragically claims the life of Perry. As they continue, the group faces an onslaught of monstrous "killer cockroaches" in the ruins of Salt Lake City, leading to a brutal encounter that results in Keegan's demise. Amid the chaos, the pair encounter two survivors, Janice, a resolute woman clinging to her humanity, and Billy, a resourceful teenager who has learned the art of self-preservation in this harsh new order. Their journey soon leads them to an abandoned gas station, where they confront a band of marauding mountain men, whom Denton swiftly dispatches with the Landmaster's firepower.
As they push forward, the Landmaster suffers a drivetrain failure near Detroit, forcing the group to seek spare parts amidst the city's desolation. Denton humorously notes their vehicle was designed to use readily available semi-truck components, a detail that underscores their plight. In their search, they navigate an expansive wrecking yard but are soon engulfed by a hemisphere-wide storm that compels them to seek refuge within the Landmaster. Just in time, they evade a megatsunami that thunders down upon them, whisking them away from solid ground.
Once the storm subsides and clarity returns to the skies, it becomes apparent that Earth is edging back toward stability. The group utilizes their amphibious vehicle capabilities to reach land and begin repairs. While working, they intercept a faint radio signal filled with music and attempts at communication. Thanks to Denton's ingenuity, he establishes contact with the source of the broadcast, which leads Tanner and Billy on a quest atop Tanner's dirt bike to uncover its origins.
Ultimately, their endeavors lead them to a surprisingly well-preserved suburb of Albany, New York, where they are embraced by the community, highlighting humanity's indomitable spirit and resilience in the face of overwhelming adversity.
