Last issue Reed Richards proposed marriage and Sue Storm accepted. Now it's their engagement party and everyone is there. Even Spidey. Sort of.
Fresh from his appearance in Amazing Spider-Man #19, December 1964, the Sandman escapes from prison along with Paste Pot Pete. As they get away in a stolen plane, they encounter the Wizard floating helplessly in the air, after his latest defeat by the Human Torch in Strange Tales #118, March 1964. They team up and realize that they could challenge the Fantastic Four as an evil counterpart if they could find an appropriate woman member.
As Reed and Sue publicly announce their engagement, the Wizard travels to a "small Mediterranean island" where there is rumored to be a woman of great power living in the caves. She calls herself Madame Medusa and her hair responds as if it's alive. The Wizard convinces her to come with him and join their group.
Somewhere across town, the villains prepare to attack (the Wizard comes up with a new costume and calls himself "the Wingless Wizard") even as Reed and Sue's engagement party gets underway at the Baxter Building. It looks like a pretty dull affair but (from left to right) the Iceman, the Beast, Professor X, the Angel, Marvel Girl, the Wasp, Giant-Man, Thor, Iron Man, Captain America, Rick Jones, and Cyclops are all there. The X-Men get a mental command from the Professor and head out. While the FF are busy saying their goodbyes to Professor X and the crew, a webbed red glove slips into a window, webbing shoots out, and a piece of cake is snagged. Spider-Man is taking advantage of the X-Men's departure to grab a little dessert for himself. "I'm sure they would have invited me if they knew where to find me so I'll just help myself to a piece of cake!" he thinks. Then he decides, "Uh oh! I'd better leave! There's some kind of ship coming!"
It's too bad that Spidey doesn't stick around. He is so sure that the ship contains guests who will nail him as a cake-stealing party-crasher that it never occurs to him that the new arrivals may be bad guys. The newly named Frightful Four attack right after the party, with all the super-hero guests gone and the FF resting up from the festivities. The Torch has left the building and is hanging out with some hot-rod buddies as the evil FF moves in and captures the other three Fantastic Four members. The Wizard ties them together, puts an anti-grav disc on the back of each one, and sets them adrift from the top of the Baxter Building. But Alicia Masters, the Thing's girlfriend, manages to fire off the Fantastic Four danger signal and the Human Torch comes running. Torchy gets back to the Baxter Building, kidnaps the Wizard and the Wizard's ship, forces the Wizard to fly it up to his teammates and saves Reed, Ben, and Sue moments before they suffocate up near the top of the atmosphere. Another battle follows with the Fantastic Four gaining the advantage until the Wizard blows up his ship creating a diversion which allows the Frightful Four to escape.
The Frightful Four return in FF #38, May 1965 and again in FF #41-43, August-October 1965. In FF #44, November 1965, Medusa is revealed to be a member of the Inhumans and leaves the evil FF. The Sandman uses his membership in the Frightful Four to make the transition from Spider-Man villain to Fantastic Four (and Hulk) villain. He doesn't meet Spidey again until Marvel Team-Up #1, March 1972. Spider-Man eventually faces all of the Frightful Four both individually with the Wizard in ASM Annual #4, November 1967, Medusa in ASM #62, July 1968, and Paste Pot Pete, now called the Trapster, in The Spectacular Spider-Man #158, December 1989 and collectively with Annihilus replacing Medusa in Marvel Team-Up #2, May 1972 (well, Annihilus is the fourth villain but it is actually a mind- controlled Spider-Man who is the fourth member of the Frightful Four), Electro filling in in Peter Parker: The Spectacular Spider-Man #42, May 1980 and FF #218, also May 1980 and Llyra taking the fourth spot in ASM #214- 215, March-April 1981.
Milestones (Landmark events that take place in this story.)
Spider-Man's arm appearance doesn't even reach to his elbow and Reed and Sue's engagement party has to be the snorer of the century but the introduction of the incredible Madame Medusa combined with the first get-together of the Frightful Four makes this one of the all-time greats. Stan and Jack start hitting their stride with this one, leading to a string of about 30 straight unforgettable FF issues.