Eddie Brock and the Venom symbiote find themselves in a state of intoxication within a bar in Mexico, continuing their escape from the chaos left in the wake of their recent confrontation with the formidable Carnage. Their situation intensifies when the murder of Patrick Mulligan captures international media attention, thrusting Eddie into the spotlight as the prime suspect. This compels him to embark on a journey to New York City, determined to prove his innocence against the mounting allegations.
This turbulent journey becomes even more perilous as an ominous entity known as a Xenophage begins to hunt down Eddie and Venom. The events surrounding them also attract the gaze of Rex Strickland, portrayed by Chiwetel Ejiofor, who is a soldier overseeing Imperium—a covert government operation stationed at the looming Area 51. Their mission focuses on capturing and examining other symbiotes that have fallen to Earth. Meanwhile, it is revealed that Mulligan, who was previously thought to be dead, manages to survive the encounter with Carnage, only to be captured by Strickland’s men after being abandoned by a wayward symbiote. He becomes bonded with one of the countless symbiotes held captive, making him a crucial asset for Strickland's inquiry into the symbiotes' mission on Earth before Strickland receives a directive to apprehend Venom.
In a tense moment while clinging to an airplane en route to New York City, Eddie and Venom face an unexpected ambush from the Xenophage, forcing them to leap into a vast desert. Venom educates Eddie about the origins of the Xenophages—creatures unleashed by Knull, the symbiote creator, tasked with retrieving a Codex forged at the moment a symbiote revives its host. Since Venom resurrected Eddie previously, Eddie now unwittingly carries this crucial Codex that the Xenophage relentlessly pursues. Following a narrow escape from both Strickland’s forces and the pursuing Xenophage, Eddie stumbles upon a nomadic family roaming the woods, who generously extend their hospitality and offer him a ride to Las Vegas. Meanwhile, Mulligan, now equipped with his own symbiote, informs Strickland of Knull's true design and the significance of the Codex, a vital fragment that can only be obliterated if either Eddie or Venom perishes.
Upon arriving in Las Vegas, Eddie and Venom encounter Mrs. Chen, played by Peggy Lu, at a lively casino. An unexpected dance moment between Venom and Mrs. Chen takes a chaotic turn when they are ambushed by the Xenophage once more. Strickland’s team arrives on the scene, successfully capturing Venom and incapacitating Eddie. At Area 51, Eddie undergoes intense interrogation, but in a twist of fate, Venom manages to break free from his confines, drawing the Xenophage's attention back to the Codex as they launch a fierce attack on the base. With a resounding call, Venom orchestrates the release of the other symbiotes held captive in the lab, allowing them to bond with new hosts and join forces to thwart the Xenophage invasion. Eddie, Strickland, and lead researcher Dr. Teddy Payne, played by Juno Temple, encounter a family led by Martin, who have also infiltrated Area 51 seeking extraterrestrial life. Realizing the imminent danger posed by Knull, who has pinpointed the Codex's location, a battalion of Xenophages is dispatched through portals to attack Venom. In a selfless act to protect Martin’s family, Eddie endeavors to lure the creatures away, ensuring their escape with the assistance of the newly bonded symbiotes.
In a moment of self-sacrifice, Venom understands that the only way to obliterate the Codex and secure the universe’s safety is to sever his connection with Eddie. With a heavy heart, Venom bids Eddie farewell and merges with the approaching Xenophages, leading them toward acid tanks. As a mortally wounded Strickland activates explosives to eradicate the creatures, Eddie loses consciousness amidst the devastating flames that engulf Area 51.
When Eddie regains consciousness in a hospital, a federal official informs him that due to his brave actions alongside Venom at Area 51, his criminal history has been wiped clean—but he is cautioned never to disclose the events that transpired. Arriving in vibrant New York City, Eddie reflects on his profound memories shared with Venom while gazing at the Statue of Liberty. In a stirring mid-credits scene, Knull ominously declares that the universe is no longer free of his looming menace. Meanwhile, a post-credit scene unfolds as a terrified bartender makes a frantic escape from Area 51, only to find a cockroach seemingly fused with the Venom symbiote, leaving viewers eager for what comes next.
