Spider-Man: Across the Spider-Verse Ending Explained - What's Next For Miles?

gamespot.com:

Spider-Man: Across the Spider-Verse is a big escalation from the first movie. Last time out, we mostly hung out in Miles Morales' home dimension--but now, Miles is going all the way down the multidimensional rabbit hole, and he's going to find some things he really doesn't like down there.

Warning: This article contains major spoilers for Spider-Man: Across the Spider-Verse, including the full details of how it ends.

Across the Spider-Verse makes its intentions known right from the start, with a lengthy opening sequence that takes place in Gwen's universe, Earth-65. We get Gwen's backstory, with the tragic tale of her universe's Peter Parker, and how his death eventually led her to the cross-dimensional Spider-Society.

Then we catch up with Miles, who hasn't seen any of the other Spider-folks in over a year. He encounters and fights a new villain named The Spot, who has dimensional portals on his body, and not long after that, Gwen shows up. She's after The Spot, but visits with Miles while she's there. She tells Miles he's not allowed to be in the Spider-Society, then tracks The Spot to a dimension where Earth is dominated by an extremely awesome Mega City called Mumbattan (that's a portmanteau of Mumbai and Manhattan).

Miles sneakily follows her through a dimensional portal and ends up fighting alongside Gwen, Spider-Woman Jessica Drew, Spider-Punk, and Spider-Man Pavitr Prabhakar as they face off against The Spot in Mumbattan. The battle results in a sort of draw, as The Spot gets what he wants, but the Spider-People manage to save everybody. However, they may have saved too many, it turns out. We'll circle back to that.

Since Miles is already with them, the gang brings Miles back to Spider-Society HQ in Neuva