Synopsis
It's 10 days since Quicksilver vanished in the Sentinels' Australian base last issue. Scarlet Witch is distraught and apparently hasn't slept since then, continually trying to find some clue to the whereabouts of her brother, or evidence of other people disappearing. Hawkeye and Iron Man try to talk her down to no avail.
The duo see house-guests Balder, Fandral, Hildegarde (a Valkyrie), Hogun, Silas Grant (a sailor from Blackworld) and Tana Nile (a Rigellian) on the way out for a night on the town. They decline to join them, and greet Black Panther who is just entering for a visit, after coming to America to see his friend Daredevil.
But the reunion is interrupted by Wanda who has picked up something that may relate to the missing Pietro. Some strange men popped up in Chile and kidnapped 3 scientists. She thinks maybe this is what happened to Pietro. Panther agrees to accompany the Avengers to investigate. Thor is here too, and Sif insists on joining the expedition in return for the team's hospitality. Captain America isn't around. But Vision arrives in time, fresh from a battle with Puppet Master and a Skrull robot left over from the Kree/Skrull War in Marvel Team-Up #5.
The assembled group fly a quinjet to Tierra Del Fuego, where some unkidnapped scientists say their compatriots were taken into a cave, which was sealed after them. Hawkeye and Iron Man blast their way in. (Iron Man comments that he's improved the reliability of his armour since his fight with the Cyborg Sinister [actually the Super-Adaptoid] in IM#51.)
The Avengers find a tunnel which leads to the Savage Land in Antarctica. (Iron Man asks Black Panther about calling himself Black Leopard. He says he did that briefly to distance himself from the Black Panther movement. But he's changed his mind.)
Suddenly they are attacked by Swamp Men under the mental control of the mutant Lupo, backed by the 4-armed Barbarus. The Avengers treat their attackers gently, until Thor scatters them with a bolt of lightning, to stop Barbarus abducting Sif.
Panther's friendship with Daredevil appears not to be casual, as does DD's connection to Ka-Zar. DD has spent enough time with each of them that he's passed on to Panther details of Ka-Zar's fight with Magneto and the Beast-Brood alongside the X-Men in (Uncanny) X-Men #62-63. Enough so that he can recognise Barbarus and Lupo, and lead his team-mates to the ruined site of Magneto's HQ.
Panther can't explain how the 2 Beast-Brood members have their powers, as they had all reverted to being ordinary Swamp Men at the end of UXM#63. DD's info-dump can't have been complete because T'Challa is surprised to find an abandoned costume of Angel's at the site. Which reminds Wanda that the Sentinels told her they couldn't find the X-Men while she was their captive in the last story arc.
Just then the Beast-Brood attack. Barbarus and Lupo are joined by Amphibius, Brainchild, Equilibrius and Gaza. Equilibrius affects Iron Man with vertigo, but Shellhead uses his armour to stay upright and knock the villain down. Brainchild leads Hawkeye to a spot carefully calculated to trap him in fallen rubble, but Clint goads him into a childish tantrum causing him to faint. Thor and Sif combine to take Barbarus out. Blind Gaza mentally tracks Scarlet Witch and traps her, but Wanda's hex makes him see with his eyes which confuses him until Black Panther decks him. (Panther says he's already dealt with his chosen foe, which by process of elimination must be Lupo.) Amphibius bounces all over Vision until the android goes intangible and the frog-man leaps through him to slam against a wall.
Equilibrius muses that he doesn't know how the Beast-Brood regained their powers, but they lost them when their creator Magneto died in UXM#63. Maybe their returned powers indicate that Magneto lives again.
Be that as it may, he decides to reuse the ploy that Magneto tried in UXM#63 and ushers in Lorelei to bewitch the male Avengers with her singing. He indicates that he will deal with the females himself. But before he can be shown up by Sif and Wanda, Vision proves himself immune to Lorelei's spell and renders her and Equilibrius unconscious with his 'hand materialising inside the body' trick.
The android Vision takes his immunity as more evidence that he isn't human and is incapable of love. So he turns away from Wanda.
Off-screen the Avengers rescue the scientists, whom the Beast-Brood had wanted to create more mutants. But of course they don't find Quicksilver.
When they return home Jarvis the butler shows Scarlet Witch a news item he has recorded of a man disappearing on a New York street. She asks the other Avengers to help her again, but Thor and Sif have already left. And Vision just sits brooding over an amulet. So Wanda stalks out with Black Panther, Hawkeye and Iron Man.