The film opens with a striking voiceover by Sir Cedric Hardwicke, warning that greedy eyes are fixated on our beautiful blue planet. These beings, who covet our clear air and abundant resources, have considered retreating to other planets within our Solar System but found them all inhospitable. The narrative hints at past cataclysms, mentioning World War I and World War II while forebodingly indicating the emergence of another threat: the war of the worlds. As both Earth and Mars align closely in their orbits, ominous attacks begin.
In Southern California, a peculiar fireball blazes its way through the sky, ultimately crash-landing in a gully nestled in the San Gabriel Mountains, a region east of Los Angeles. Firefighters promptly extinguish the flames, yet authorities are left bewildered by the elongated, cylindrical object that caused the disturbance. The object not only fascinates tourists but also piques the interest of Dr. Clayton Forester (Gene Barry) from the Pacific Technical Institute. While many perceive it as a potential tourist attraction or hidden treasure, Forester recognizes the sinister truth: this is no ordinary meteor. Its lightweight composition and high temperatures suggest something far more alarming—it is indeed radioactive.
Dr. Forester seeks refuge in the local town under the hospitality of Pastor Matthew Collins (Lewis Martin) and his niece, Sylvia van Buren (Ann Robinson). As the investigation unfolds, three curious men approach the mysterious probe that emerges from the cylinder, only to meet a gruesome fate as it unleashes a devastating heat ray, incinerating them instantly. As chaos erupts, the local power grid collapses, watches begin to malfunction, and strange magnetic anomalies arise, indicating something supernatural at play. Determined to unveil the truth, Forester investigates further but discovers a terrifying reality: they are confronting an extraterrestrial menace.
With a sense of urgency, Forester notifies the military after witnessing the horrifying aftermath surrounding the cylinder. At the same time, a series of fireballs descend across the globe, reinforcing the need for immediate action. Marines and Air Force personnel converge with heavy artillery, but as they prepare to engage, Collins imprudently steps forward, imploring for peace. In a shocking turn, the lead swan probe retaliates, burning him alive right before Sylvia’s horrified eyes, prompting an all-out assault on the Martian craft.
As the battle ensues, artillery fire proves futile against the Martians' magnetic shields. Major General Mann (Les Tremayne) and Marine Colonel Heffner (Vernon Rich) witness the disintegration of their forces as they battle the invaders, who retaliate with merciless heat rays and energy blasts. In the midst of this tension, Forester and Sylvia attempt to escape in an aviation vehicle but crash-land, narrowly evading the relentless Martians surrounding them.
Finding temporary refuge in a dilapidated farmhouse, Sylvia reveals her anxieties and feelings of loss due to her uncle's death. Just as their intimate moment unfolds, disaster strikes as yet another cylinder crashes, rendering Forester unconscious. When he awakens, they realize the entire area is besieged. In a desperate attempt to fend off the intruders, Forester bravely battles a Martian crewman, but their plight intensifies as more cylinders descend worldwide, signaling the Martians’ ruthless objective to exterminate humanity.
Back in Washington, preparations for an atomic bomb strike on the Martian stronghold intensify. Yet, upon delivering a blood sample and alien equipment to his colleagues at Pacific Tech, Forester discovers that the Martians' blood is anemic, hinting at a possible weakness. As panic surges, the proposed bombardment fails to penetrate the Martian defenses, compelling a mass evacuation of Los Angeles.
Despite the chaos, Forester devises a plan to use biological weapons against the invaders and rallies surviving scientists to aid in the effort. However, hope fades further as looters disrupt their preparations, and the swan probes commence systematic attacks. Forester fights to locate Sylvia amid the turmoil, leading him to various churches where desperate prayers rise. In a moment of relief, he finally reunites with Sylvia, but their encounter is interrupted by a new wave of Martian aggression.
As luck would have it, the Martians suffer an unexpected turn of fate. One of the swan probes experiences a technical failure and crashes. In a shocking twist, observers realize that the Martians' immune systems could not cope with Earth's bacteria, leading to their downfall. One by one, the once-feared craft plummet as the biological onslaught overwhelms them.
Ultimately, humanity's survival hinges not on advanced weaponry but on the simple fact of our planet's rich biodiversity, which the Martians could not withstand. The once daunting invasion crumbles swiftly, leaving behind silence and disbelief as the threat has been vanquished more rapidly than anticipated. The tale serves as a potent reminder of resilience as the world emerges from the shadows of imminent peril.
