Thor returns from Asgard and finds himself in an alternate version of House of M.
Dr. Doom is now in control of the world, is married to the Black Widow and Hawkeye, Falcon and Spider-Man make up what is called the Defenders.
In Thor's first encounter on this new world, he loses his uru hammer but the Defenders escape to what used to be the shield Helicarrier. Enter Doom, who captures Thor and the Defenders in short order.
They are brought to what was once Avengers Tower and Thor finds out that Doom has gone back in time, "rescued" Tony Stark and Bruce Banner and kept them gaining powers, thus from "becoming heroes." It seems like they serve him willingly.
Not willing to go along with Doom's desire to conquer other worlds through Mjolnir, Thor and the Defenders are prepared for a public execution. It is then Natasha, the Punisher in disguise, Tony Stark and Bruce Banner show their true selves, as true heroes of this world, even without powers.
Stark releases the hammer to Thor's command and then Natasha startles her husband by saying she would rather be ... a "widow" than his bride! Meanwhile an iceberg holding the body of Steve Rogers falls from a Doom display rack and here comes Captain America!
Dr. Doom is quickly and summarily defeated and before he can go through time again, he is conquered by Bruce Banner who claims to be "the smartest one there is."
The heroes, realizing Thor was outside of time and space when this occurred, send him back in time to keep Doom from repeating his chronal villainy. Thor does, secretly breaking the machine and leaving Doom believing the machinery and plan a dismal failure.
Doom himself destroys the time machine!
This was a very enjoyable and thoroughly entertaining edition of Avengers Assemble. It would be very good as a comic book ... and was. Remember House of M?
Frankly, I enjoyed this much more.