Full story
After Mysterio tells the world that Peter Parker is Spider-Man and frames him for murder, Peter, MJ, Ned and Aunt May are questioned by Damage Control. Lawyer Matt Murdock gets the charges dropped, but life becomes a nightmare for the three teens. When all three get rejected by MIT because of the controversy, Peter goes to the Sanctum to ask Doctor Strange for help.
Strange starts a spell to make everyone forget Peter is Spider-Man. In the middle of it, Peter keeps asking for exceptions: MJ, Ned, May, Happy. The changes wreck the spell, and Strange contains it in time, but the damage is done. People from other universes who know who Spider-Man is start showing up. On a bridge, Doctor Octopus attacks Peter and steals some of his suit's nanotech, until he realizes this isn't the Peter he knows. Then come the Green Goblin, Electro, the Lizard and Sandman.
Strange wants to send them all back, but Peter learns that many of them would return only to die fighting the Spider-Man of their world. He decides to cure them first. He steals the spell, traps Strange in the Mirror Dimension and takes the villains to Happy's apartment. It works on Octavius, but the Goblin persona takes over Norman Osborn again. He turns the other villains against Peter and fatally wounds May. Before she dies, she reminds Peter that with great power there must also come great responsibility.
Ned finds out he can open portals with Strange's sling ring and, while looking for Peter, brings in two other Peter Parkers: Tobey Maguire's and Andrew Garfield's. The three share their losses and decide to finish the job. At the Statue of Liberty, they cure the Lizard and Sandman, and Octavius helps cure Electro. Ned frees Strange by accident. The Goblin smashes the box holding the spell, and the multiverse starts to crack wide open, pulling in more people who know Peter's secret. Peter, full of rage, almost kills the Goblin, but Maguire's Peter stops him. Garfield's Peter catches MJ in a fall, the way he couldn't with Gwen, and the Goblin gets his cure.
To seal the multiverse, Peter asks Strange to make the whole world forget Peter Parker exists, MJ and Ned included. He promises to find them again. Everyone goes back to their universes. Two weeks later, Peter visits the coffee shop where MJ works but stops himself from introducing himself so he won't put her in danger again. At May's grave, he runs into Happy, who doesn't remember him either. Alone in a bare apartment, Peter sews a new suit and goes back to protecting the neighborhood. In a credits scene, Eddie Brock, pulled into this universe by the spell, gets sent back but leaves a piece of the symbiote behind. That is left open.