With the aid of the new recruit , the heroes must come together once again to rescue Captain America before Red Skull can transfer his mind into Captain America's body. When Maximus gets Inferno angry, he loses control of his powers and Attilan burns to the ground. The Avengers must defeat him as well as new threats like 's and. Captain America and Black Panther head to Hong Kong where they find working on the Talisman of. They encounter , , and along the way. At the same time, he tries to teach Ms. The last two episodes detail the escape of Thanos by the Black Order and their attack on Earth.
Before Bask can have Black Panther executed, White Wolf rescues Black Panther and they run off with Ulysses Klaue as their hostage. Though Ultron attempts to escape the suicidal death trap while converting Iron Man, Arsenal overrides Ultron long enough to blast off to the sun while Iron Man is retrieved by Thor. After helping Captain America take out Crossbones, T'Challa makes off with Captain America's shield claiming it was stolen property. Now its up to Hawkeye in Thor's body to convince Iron Man in Hawkeye's body that they have to become more than perfect. Meanwhile, Shuri and Zemo work to eliminate the Shadow Council's virus from Wakanda's computer systems.
Falcon must prove to himself and a skeptical Hawkeye that he's still a hero when preventing the Shadow Nyx from overtaking Vanaheim and restarting the great light that kept them at bay. Tracking Zemo to Château le Fay in Switzerland, Black Panther finds that Baron Zemo is planning to destroy his father's files before it falls into the wrong hands. Marvel to obtain it while Black Bolt and Medusa are arguing as they also deal with the shapeshifting Princess Zanda of Narobia who is on the Shadow Council. Now Doctor Strange and the remaining Avengers must find a way to defeat Agamotto. The Avengers then decide to help get all Inhumans registered while working to defeat Maximus. Vision repairs this Skullbot and keeps it as a pet. As Thor is looking for a weapon that is worthy of a prince, he hitches a ride on Yemandi's Cutter and accompanies Yemandi on a mission to find Bashenga's Core.
In retaliation for Madame Masque's laser being fired on Atlantis by Bask, Elanna and Tiger Shark lead the Atlanteans into attacking in order to get to Bask. When Hawkeye tells the other Avengers about this, the rest of the Thunderbolts must decide on whether they should continue to work with Zemo or help the Avengers stop him. Now that Captain America is out of the Crown's pocket dimension, he figures out that Black Widow was actually Princess Zanda in disguise. At the same time, Captain Marvel and Black Panther argue over who's leader of the new team. The rest of the season details the arrival of the and their confrontation with the Avengers. Black Panther discovers that Ulysses Klaue is behind the attacks with the help of some mercenaries and mutated sonic-emitting bats nesting in Vibranium caves for centuries.
During fight with Ultron, Tony is able to inject Ultron with Destroyer Malware with help of his team mates. Captain America discovers that the trespasser is none other than his old partner now the Winter Soldier who is back seeking revenge on Red Skull. Afterwards, the Avengers must stop from building and unleashing his secret weapon with stolen A. When Morgan le Fay also targets Bashenga's Core to use in her plot to rule the world and transforms Thor into a frog, Yemandi and Thor must work together to reclaim Bashenga's Core and defeat Morgan le Fay who has reshaped Bashenga's Core into the Crown. This causes Black Panther and Ms. Marvel a tour of Avengers Tower, they end up dealing with Iron Man's old enemy whose awakened Inhuman abilities have enhanced his phasing abilities as he plans to steal Friday while disabling each of the Avengers one by one.
When Ultron in the Destroyer Armor arrives on Earth, Vision must help the Avengers defeat Ultron. She manages to save them but the gems end up corrupting her. When a guilt-ridden Thor helps Black Panther take down Leader when the Avengers arrive, Leader summons his new incarnation of the Cabal consisting of , , , and to fight the Avengers while taking advantage of Iron Man not being there. Note 2: Despite airing during Season 4, the timeline of this episode takes place during Season 3. At the end of episode, it is seen that Ultron's first mission of disassembling the Avengers is done successfully.
Under Captain America's suggestion, Hawkeye puts Ant-Man through an Avengers training course on Monster Isle to determine if he is cut out to be a member of the Avengers. During the battle between the Avengers and the Zemos, Hawkeye, Black Widow, and Falcon are sent to 1943 where they work with a younger Steve Rogers to make an antennae that would signal the time machine. The Avengers discovers they are more than eight heroes. With Captain America still recuperating and Shuri keeping an eye on Bask, Black Panther frees White Wolf in order to get into Atlantis and stop the Shadow Council from starting a war. The unlikely duo of Hulk and Black Widow is the last line of defenses between the city and the Hulk-Vengers before the virus causes them to detonate. After Ulik briefly breaks out, Vision ends up taken over by Ultron until Vision fights his control enough for Ultron to take control of the Destroyer Armor. When the Korbinite Jeter Kan Too of New Korbin begs the Avengers to save them from mysterious invaders, the team discovers that Thanos and his Black Order are plundering New Korbin.
But he has to stay in the dimension so Ultron can't leave. After Red Skull's failed mission destroys Avengers Mansion which causes the Avengers to relocate to , he sends out invitation to multiple villains to join his. M base using his Ultron detector, which he does not share with his team. When Toomes gets his Vulture suit back and decides to tie up some loose ends, Black Panther must work with Spider-Man to defeat Vulture. Everything seems to be going good until Ultron orders his sentries to destroy all life on Earth. With the Avengers reunited, Captain America and Iron Man invite Ant-Man to their team.