After the past, present and future, what's left but the end of the universe? Back from dinosaur days, the FF are themselves targeted for extinction — but will a new FF render them obsolete? Cross-genre champions face alien invaders at the center of the Earth, as only Walter Simonson could conceive it! Then, team members get medical treatment from none other than Doctor Doom, whose split-second war with Mister Fantastic leads the Time Variance Authority to rear their faceless heads! Guest-starring Ghost Rider, the Hulk, Spider-Man and Wolverine! Collecting FANTASTIC FOUR #347-350 and #352-354.
— Description from Comic Vine community (comicvine.gamespot.com).
