Full story
Miles Morales is 13, lives in Brooklyn and just started at an elite boarding school he never asked for. His dad, Jefferson, is a cop who sees Spider-Man as a menace. His uncle Aaron is the one adult Miles feels at ease with. One night Aaron takes him to an abandoned subway station to paint graffiti, and a radioactive spider bites the kid.
Over the next days his powers kick in with no control: his hands stick to everything, he turns invisible and gives off shocks. Going back to the station, Miles finds his Earth's Spider-Man, Peter Parker, fighting the Green Goblin inside a giant collider. The machine belongs to the Kingpin, Wilson Fisk, who wants to open portals to other universes and bring back his wife, Vanessa, and son, Richard, who died in a crash. Peter hands Miles a flash drive to shut the collider down, but the Kingpin kills him. The whole city mourns its hero.
The collider has already pulled in people from other worlds. An older Peter B. Parker, divorced and worn out, agrees to train Miles. They break into Alchemax to build a new drive and run into Dr. Olivia Octavius, Doctor Octopus. Gwen Stacy, the Spider-Woman of another Earth, helps them escape. At Aunt May's house they meet Spider-Man Noir, Peni Parker with her robot and Spider-Ham. All of them are slowly glitching apart and need to get home. They think Miles isn't ready.
The worst blow comes when Miles learns his uncle Aaron is the Prowler, the Kingpin's enforcer. Aaron can't bring himself to kill him and gets shot by Fisk. He dies in his nephew's arms. Jefferson shows up and blames the new Spider-Man. Locked in his room, Miles hears his dad say through the door that he believes in him. That's the push he needed: he takes control of his powers, grabs a suit from Aunt May, spray-paints it his own way and takes his leap of faith off a skyscraper.
In the final battle, Miles sends the other heroes home, including Peter B., who wanted to sacrifice himself in his place. Then he takes on the Kingpin alone, slams him into the kill switch and destroys the collider. Fisk is arrested, Jefferson starts to see Spider-Man differently and Miles takes up the mantle. Gwen finds a way to reach him from her universe. The post-credits scene shows Miguel O'Hara, Spider-Man 2099, hopping between worlds. That comes back later.