Arrested for his crimes, Eddie Brock aka Venom was locked in a cell with savage killer Cletus Kasady. When he made his escape, the symbiote "gave birth" to a symbiote spawn which possessed Cletus. Altered by being born on Earth, the symbiote became twisted and together they became...CARNAGE! Proving too hard to handle for Spidey alone, he must now seek the help of the most unlikely of allies...Venom!
Carnage has invaded the offices of the Daily Bugle to strike at the city's greatest crusader for law and order-J. Jonah Jameson! Before he can do the deed, Carnage is interrupted by Robbie Robertson and takes off with Jonah in tow.
Meanwhile, as they race to the Bugle, Spidey ponders over his alliance with Venom, wondering if it's a wise move. They arrive to a less than warm reception by the police talking to Robbie in Jonah's office. It takes some convincing, but the police let them go in the direction Robbie tells them Carnage went citing he needed a bigger audience with which to make his message of chaos heard.
Along the way, Spidey has Venom tell him about Kasady when they find a woman plowed through a wall. One of Carnage's random killings. Spidey has to restrain Venom from beating information out of bystanders when he spots a poster for the perfect venue for Carnage to do his thing. The heroes race to Madison Square Garden where Carnage interrupts a metal concert and preaches his philosophy on how easy it is to kill people.
Before audience members can partake of Carnage's teachings, Spidey and Venom crash the party and get Jonah out of his clutches. They take the battle to him and get him out of the Garden. Carnage beats a hasty retreat for the subway, killing pedestrians in his path as he goes. They pin him in a tunnel only to be struck down by Carnage's moves and weapons. Even a dose of the third rail can't seem to stop him.
Carnage decides to handle his business while he can and returns to the Garden. Venom and Spidey are close behind where they find Jonah captured once again. Carnage attacks, and while Venom keeps him busy Spidey frees Jonah and heads up to the control booth of the stadium. Modifying the PA system, he turns it on to generate the frequency symbiotes hate, taking Carnage down once and for all.
Spidey joins Venom with the speakers still blaring, but Venom's hatred for Spidey gives him the strength to take him down regardless. What he didn't count on was the Human Torch and Mr. Fantastic waiting in the shadows with a new sonic gun, making Venom more convinced than ever that Spidey was never innocent. As Venom is being carted to the Vault in a special holding cell designed by Mr. Fantastic, Jonah takes a jab at Spidey by saying "Captain America would have kept his word." Spidey grabs Jonah and informs him Cap would've found a better way because he's a legend, while Spidey is just a man who has to live with the choices he makes.
Meanwhile in East Germany, two people are about to board a plane that will shake up Peter's life.