The previously page tells us things that are actually intertwined with a long flashback that starts this issue. So I'll just lump it all together in order.
In New Avengers #1-3 the Illuminati learned of the threat of incursions by Earths from alternate universes. On each incursion 1 of the 2 Earths must be destroyed to save both universes. Captain America refused to accept that they had to kill a planet to save their own. He suggested they use the Infinity Gems which they were guarding. When an incursion happened Cap successfully used the Gems to repel the other Earth and separate the universes. But the Gems then self-destructed, except the Time Gem which disappeared.
With this option gone the other Illuminati wanted to plan ways to destroy other Earths if necessary. Cap refused to compromise his principles - he believed they would always find another way. He said if they built weapons of destruction they would eventually use them. The team expected this, and Dr Strange cast a spell to make Steve Rogers forget all about incursions, and the Illuminati continued to operate in secret from Wakanda's Necropolis.
In #1 of this series Steve woke from a dream of the Illuminati members looming over him. And Tony Stark told him of his plan for a bigger Avengers team to meet bigger threats. (And last issue Bruce Banner worked out what had been going on, and deduced that Stark had expanded the Avengers to take care of things like the recent Infinity event, while Tony concentrated with the other Illuminati on the incursion problem. Bruce was inducted into the Illuminati at the end of last issue.)
Now Steve Rogers has another dream about all this (apart from the Banner bit). And he wakes up remembering what happened.
In Avengers Tower Hawkeye and Black Widow are scanning for signs of the evil alternate-reality Avengers that plagued this book in #25-27, but can't find anything. (Apparently Tony Stark hasn't passed on the information he got from Bruce Banner last issue, that AIM has sent the evil duplicates to another timeline.)
Angry Cap asks them to accompany him to confront Stark. He's also recruited Thor as backup, and Thor has brought along Hyperion and Starbrand. They break down the door of Tony's lab, even though it wasn't locked.
Steve correctly suggests that Bruce worked out last issue that Tony has been lying to them all for a long time. (Rogers obviously doesn't know that Banner has been taken to join the Illuminati. But this confirms the idea that Cap wasn't in on the scam when Stark imprisoned the alternate Banner for Hulk's crimes last issue.) Tony tries to play the innocent. But Cap reveals that he remembers everything.
Steve now explains to the other Avengers all about the incursion threat and the Illuminati's plans. Stark admits it, but protests that they haven't had to destroy any alternate Earths yet. But Steve also works out that the expanded Avengers were all part of Tony's secret plan.
Stark now armours-up, and also calls on a horde of drone Iron Man suits. The obligatory battle ensues. But then the missing Time Gem pops up in Cap's hand. It now shatters like the other Gems did in NAv#3. And the next thing you know we're 48 years in the future.