The story begins with a flashback to months ago the Janitor for Mid-town High school kills Roger Harrington the school principal. back to the present day, we see Spider-Man, the Sandman and Dennis driving around New York trying to find out the true Murderer of the Ben Parker from an alternative timeline and the Spider-Man of the future, and to save Sandman's father Floyd Baker from being executed.
You're from the future. His future. It was the only way you could know that the other Spider-Man was from 2211. And since there's been a future Spider-Man... and future Hobgoblin... Why not a future Chameleon?