Complex sentence: Their plot involved them capturing Spider-Man and impersonating the web slinger to infiltrate the Baxter Building, taking out the Fantastic Four one at a time, although they were defeated when Spider-Man escaped and came to Mister Fantastic's aid.
Split into simpler sentences: Their plot involved them capturing Spider-Man and impersonating the web slinger to infiltrate the Baxter Building, taking out the Fantastic Four one at a time. Although they were defeated when Spider-Man escaped and came to Mister Fantastic's aid.