Full story
After a quick trip to another universe, Eddie Brock and Venom are back in their own world and end up drunk at a bar in Mexico. The trouble is they're wanted now: Eddie is the prime suspect in Detective Patrick Mulligan's apparent death. The plan is to get to New York and clear his name. In a scuffle with some thugs, a piece of Venom gets left behind at the bar.
Far away, Mulligan is alive. General Rex Strickland runs Imperium, a secret program at Area 51 that captures symbiotes that have landed on Earth. Scientists Teddy Paine and Sadie Christmas study the aliens and believe they could help humanity. Meanwhile, on the symbiotes' home world, their creator, Knull, is still imprisoned and sends out the Xenophages, monster hunters, to find something called the Codex.
On a flight to New York, a Xenophage attacks the plane and Eddie and Venom crash in the Nevada desert. Venom comes clean: when he brought Eddie back from the dead, he created the Codex, the key that can free Knull. The Codex only disappears if Eddie or Venom dies. From then on they have to avoid transforming, because every time Venom comes out, the signal draws the monsters. They hitch a ride with an alien-obsessed hippie family led by Martin Moon, who dreams of seeing Area 51. In Las Vegas, Eddie reunites with Mrs. Chen, who dances with Venom in a hotel room.
The Xenophage and Strickland's soldiers catch them on the road. Eddie and Venom are split up and taken to Area 51. There, Sadie frees Venom, who rejoins Eddie just in time after Strickland shoots him. The new transformation brings in more monsters. Mulligan, bonded to a symbiote, gets devoured. Venom frees the symbiotes locked up at the base, and they bond with the scientists to fight off the invasion.
The Xenophages keep coming, and Venom realizes there's only one way out: die to destroy the Codex. He says goodbye to Eddie, spreads himself over the monsters and drops into a vat of acid. A wounded Strickland changes sides and sets off grenades to take out the rest. Eddie wakes up in a hospital with his record wiped clean in exchange for silence, and goes alone to the Statue of Liberty, the way Venom always wanted. In the mid-credits scene, Knull warns that the universe is no longer safe. In the final scene, the bartender from Mexico walks out of the base's ruins, and a cockroach crawls past a broken vial holding what's left of Venom.