After a brief introductory sequence showing the team taking down Sandman and fusing him into glass, they go to New Salem with Franklin’s governess Agatha Harkness, where magical evil conjures up some strong villains and they fight and fight. Franklin Richards manifests his undefined powers again, to save the day.
I think this is the first time he uses them since Reed Richards de-powered him a while back.
We also get to see a bunch of other Marvel heroes showing up trying to pierce a magical forcefield that surrounds the city—this is a plot device that was used a lot in the late 1970s/early 1980s, and it was always a good way to crowbar in some cameos.
Marv Wolfman’s work on FF was never great, but when he’s working with Perez it gets much better.