The full story
Venom introduces Eddie Brock as an investigative journalist in San Francisco. He has a great career and a fiancée, Anne Weying, a lawyer whose firm represents the Life Foundation. When Eddie confronts Life Foundation CEO Carlton Drake on camera about illegal human experiments—using confidential information he stole from Anne's laptop—he loses everything. Fired from his network, dumped by Anne, and blacklisted from journalism.
Carlton Drake has recovered alien organisms—symbiotes—from a crashed space probe. He believes symbiotic bonding between humans and these organisms is the key to human survival in space. In practice, his experiments kill every test subject. The symbiotes are incompatible with most human hosts, consuming them from the inside.
Six months later, Dr. Dora Skirth, a Life Foundation scientist horrified by the body count, reaches out to Eddie. She helps him break into the facility to gather evidence. During the infiltration, Eddie accidentally bonds with the symbiote called Venom. The organism is massive, liquid-black, with fangs and a long tongue—and it is sentient, speaking directly into Eddie's mind.
The bonding is initially hostile. Venom is hungry—craving brains, chocolate, and living flesh. Eddie's body is being consumed as they adjust. But Venom is also a loser on his own world—a reject among symbiotes—and he recognizes something in Eddie's stubbornness that he respects. They develop a bickering buddy-comedy dynamic: Eddie insisting on rules (no eating people), Venom constantly pushing boundaries.
Drake, meanwhile, bonds with Riot—a far more aggressive symbiote leader who crash-landed separately and worked its way to San Francisco by jumping between hosts. Riot's plan is to use a Life Foundation rocket to return to the symbiote homeworld and bring back an entire invasion force. Drake, fully consumed by Riot, agrees.
Anne and her new boyfriend Dan Lewis (a doctor who helps identify the symbiote's weaknesses—fire and high-pitched sound) aid Eddie. Anne briefly bonds with Venom to save Eddie in a sequence that cements the symbiote's willingness to protect its host.
The climactic battle at the launch pad pits Venom against Riot. Riot is stronger, but Venom is more cunning. Eddie and Venom destroy the rocket, killing both Drake and Riot in the explosion.
Afterward, Eddie and Venom agree to stay bonded. Venom will protect Eddie; Eddie will provide hosts. They establish ground rules: only eat bad people. The film ends with Eddie returning to journalism and Venom as his secret partner—the beginning of the Lethal Protector.
A post-credits scene introduces Cletus Kasady, a serial killer imprisoned at San Quentin who tells Eddie, "When I get out of here—and I will—there's gonna be carnage."