I am Ixar, from the star system Sirius... and I am engaged in intergalactic warfare with powerful foes! As for your puny planet, it means nothing to one such as I! It is a mere pawn in a struggle begun centuries ago!
The Scarlet Witch returns, and she explains that Quicksilver has been kidnapped by a UFO. Hawkeye tries to apply Black Widow for membership, but Goliath refuses. The Avengers fly to the Balkans, accompanied by the Black Widow. There they discover a huge computer, named Ixar, draining information from the village's Burgomeister. Ixar's plan is to extract the powers from the Avengers and use it to make special Ultroids. They also discover Scarlet Witch to be a fake Ultroid called Ultrana. Ultrana and the Ultroids attack the Avengers, capturing them. As the Black Widow is not an Avenger, she is sent to be destroyed.
Notes
Quicksilver and Scarlet Witch were last seen briefly in Uncanny X-Men 27. They were contacted briefly by Professor X.
This is the first appearance of Ixar and his Ultroids.
Page 2: In the flashback, Mr. Burgomeister says that the towns hospitality was to make up for denouncing and driving Pietro and Wanda away because they were mutants. This event was originally depicted in Uncanny X-Men #4.
Page 5: Cap explains that they returned from Central America - In Avengers #34-35 they battled the Living Laser, in issue #35 they had traveled to the Central American nation of San Marco to battle the villain.
In an argument over Black Widow joining the Avengers, Goliath mentions that Black Widow recently teamed up with Power Man and Swordsman to attack the Avengers, indeed she did in Avengers #29-30, but she was brainwashed by Communists.
Page 6: Further into his argument with Hawkeye about Black Widow joining Goliath comments that he doesn't want the Avengers to become a "Rest home for retired villains" this is a slight towards Hawkeye, Quicksilver and Scarlet Witch who prior to joining the Avengers in issue #16 were all villains, Hawkeye first battling Iron Man back in Tales of Suspense 57, and Scarlet Witch and Quicksilver being members of the Brotherhood of Evil Mutants in Uncanny X-Men 4.
Hawkeye retorts with how Goliath was on "vacation" this is a reference to Goliath taking a leave of absence from the Avengers from Avengers #18-28.
Cap breaks it up and tells them their nerves are on edge since their battle against the Laser, another reference to Avengers #34-35.
Page 7: Scarlet Witch (or rather her impostor) asks Goliath and Hawkeye if their argument is how they greet a returning Avenger. Scarlet Witch and Quicksilver have been on leave from the Avengers since Avengers #30 when they left to return to their home land of Transia after they realized their powers were fading and figured returning to their home would recharge their abilities.
Page 15: Writing error, when Hawkeye calls out to Captain America after Cap's capture, Hawkeye calls him "Web-Head". "Web-Head" is the nickname of Spider-Man. Cap's nickname (or at least what Hawkeye calls him) is "Wing-Head." File:Avengers vol 1 36 error.png
Page 18 error
Page 18: Art error, Captain America appears captured next to Hawkeye, even though he was not captured by the Ultroids.
Captain America, Goliath, Wasp, Hawkeye, Scarlet Witch, Quicksilver, Black Widow, Ixar and the Ultroids are all seen again next issue.
Last issue, when Steven Rogers spun around and said "You!", Roy Thomas originally wanted the stranger to be Iron Man and Thor, wanting to return to the Avengers. Stan Lee didn't want it, because it would be hard incorporating two major characters with their own series, so Roy went with the Scarlet Witch and brought her and Quicksilver back. Another reason for this was because Roy had a feeling that Stan was going to ask for the return of Quicksilver and Scarlet Witch sooner or later.
Trivia
The title "Burgomeister" is a spelling mistake; the German word for mayor is "Bürgermeister".
I am Ixar, from the star system Sirius... and I am engaged in intergalactic warfare with powerful foes! As for your puny planet, it means nothing to one such as I! It is a mere pawn in a struggle begun centuries ago! 
