Collects Fantastic Four (1961) #176-191.
*THE FANTASTIC FOUR VS. SALEM'S SEVEN IN A SCINTILLATING SEVENTEENTH MASTERWORKS!
The Fantastic Four continue their explorations into the impossible confronting none other than the Impossible Man! From a tale that rampages through the Marvel Bullpen to the return of the Frightful Four, he’ll both torment and team-up in an attempt to make our heroes a Fantastic Five! Then, Reed Richard is replaced by his evil Counter-Earth counterpart. It’s a saga so epic in scope Thundra, Tigra, the Mad Thinker and Annihilus are pulled into it as Reed battles for his life in the heart of the Negative Zone. With little time to rest, our heroes must then battle through the Elminator, Salem’s Seven, Klaw and Molecule Man in a series of struggles that may tear apart the F.F. forever! *Source: marvel.com