Fantastic Four (1961 1st Series) #191
"Four No More!" Written by Len Wein. Pencils by George Perez. Inks by Joe Sinnott. Cover by George Perez and Joe Sinnott.
Reed, Sue, Ben, and Johnny say their goodbyes to one another and depart the Baxter Building, but the former leader of the FF decides to stay behind and watch the (phony) SHIELD agents box up his scientific equipment. When Reed gets suspicious of their activity, the Plunderer makes his move!