Plot
While exploring space for new habitable worlds, a probe belonging to the bio-engineering corporation Life Foundation discovers a comet covered in symbiotic lifeforms. The probe returns to Earth with four samples, but one escapes and causes the ship to crash in Miri. The Life Foundation recovers the other three and transports them to their research facility in San Francisco, where they discover that the symbiotes cannot survive without oxygen-breathing hosts, which often fatally reject the symbiosis. Investigative journalist Eddie Brock reads about these human trials in a classified document in the possession of his fiancée Anne Weying, an attorney preparing a lawsuit defense for the Life Foundation. Eddie confronts Life Foundation CEO Carlton Drake about the trials, leading to Eddie and Anne both losing their jobs. Consequently, Anne ends her relationship and engagement with Eddie.
Six months later, Drake's symbiosis trials are closer to success, although one of his symbiotes dies due to carelessness. Eddie is approached by Dora Skirth, one of Drake's scientists, who disagrees with his methods and wants to expose him. She helps Eddie break into the research facility to search for evidence, and he learns that an acquaintance of his, a homeless woman named Maria, is one of the test subjects. Eddie attempts to rescue Maria, but the symbiote possessing hertransfers to his body without him realizing, leaving her dead. Eddie escapes and soon begins displaying strange symptoms. He reaches out to Anne for help, and her new boyfriend, Dr. Dan Lewis, discovers the symbiote on examining Eddie. Drake exposes Skirth to the remaining captive symbiote, killing both. This leaves the symbiote inside Eddie as the only known surviving specimen.
Drake sends mercenaries to retrieve the symbiote from Eddie, but it manifests around his body as a monstrous creature that fights off the attackers. It later introduces itself to Eddie as Venom and explains that the comet is searching for planets where the symbiotes can possess and devour the inhabitants. Venom offers to spare Eddie if he helps the symbiotes achieve their goal, and Eddie uses the superhuman attributes that the symbiote imbues him with. Eddie breaks into his old workplace to turn in evidence of Drake's crimes but is surrounded by SWAT officers. Anne sees him transform to escape and takes Eddie to Dan's office, where they explain that the symbiote is rotting Eddie's internal organs. Eddie notes that the symbiote has two weaknesses: high-pitched noises and fire. Although Venom claims the organ damage can be reversed, Anne uses an MRI machine to separate him from Eddie, whom Drake's men then capture.
Meanwhile, the fourth symbiote, Riot, makes its way from Malaysia to San Francisco by hopping from body to body. It bonds with Drake, who agrees to take Riot in a Life Foundation space probe to collect the rest of the symbiotes and bring them to Earth. Anne reluctantly bonds with Venom so they can free Eddie. When Eddie and Venom are bonded again, the latter promises that it has been convinced to help protect the Earth from his kind through its interactions with Eddie, and the pair attempt to stop Riot and Drake with Anne's help. After a lengthy battle, Venom damages the probe as it takes off, causing it to explode and kill both Riot and Drake. After the incident, Eddie returns to journalism, while Anne believes Eddie is no longer bonded to Venom after this, and that Venom also died in the explosion. However, the pair remain secretly bonded and set out to protect San Francisco by devouring criminals.
In a mid-credits scene, Eddie is invited to interview incarcerated serial killer Cletus Kasady, who promises "carnage" when he escapes.
