The full story
A year after the collider, Miles Morales is juggling Spider-Man with a life his parents think is falling apart — grounded, secretive, and slipping in school. Gwen Stacy, now working with a multiversal task force after the fallout from her own world, crosses into Miles's dimension chasing the Spot, a villain whose body is covered in portals he can step through at will and who Miles dismisses at first as a joke.
Miles and Gwen follow the Spot across universes, through Mumbattan (Earth-50101, home to Spider-Man India Pavitr Prabhakar) and eventually to Nueva York (Earth-928), where Gwen's task force is based: the Spider-Society, a huge multiversal organization led by Miguel O'Hara, Spider-Man 2099. Miguel explains that every Spider-Person's universe runs on fixed "canon events" — moments, like the death of a police captain close to Spider-Man, that have to happen or the universe itself starts to unravel.
Miles learns the hard way that one of those events is about to hit him personally: his father Jefferson, about to be promoted to police captain, is due to die protecting Spider-Man, exactly like the canon event Miguel described. Miles refuses to accept it and fights his way out of the Spider-Society's custody rather than let it happen. In the process, Miguel reveals the harder truth: Miles was never supposed to be Spider-Man at all. The spider that bit him crossed over from Earth-42 — where a version of Miles exists, radicalized into that world's Prowler, having never been bitten himself.
Miles escapes with help from sympathetic allies inside the Spider-Society, but ends up flung to Earth-42 instead of home. There, Jefferson is already dead, and Earth-42's own bitter, orphaned Miles — now the Prowler — corners him alongside that world's Uncle Aaron, still alive here. As the Spot, now vastly more powerful, prepares to strike at Miles's own Earth-1610, Gwen defies the Spider-Society and rallies other Spider-People to go after Miles, leaving the fight, and Miles's fate, unresolved for the sequel.