...And Time, the Rushing River...
Returning from their adventure back in time to World War 2 (In Avengers #56 Cap felt the need to use Dr. Doom's time machine to go back in time to ensure that his partner Bucky had died during their final battle against Baron Zemo) the Avengers find that their Aerocar is missing. Walking back to their headquarters they find that the place looks oddly different, yet familiar, and set with defenses that they had changed years ago. Entering the briefing room they come face to face with the original Avengers: Iron Man, Thor, Giant-Man, Wasp, and the Hulk. Although both parties are confused a battle erupts when Goliath tries to unmask Giant-Man and is shocked to find it isn't an impostor -- it's really him. The original Avengers manage to force the "new" members into retreat, and they seek refuge in a nearby subway tunnel to try and figure out what's going on. They deduce that perhaps their accidental tampering of history during World War II had caused a time paradox that has caused their current predicament.
Meanwhile, the original Avengers are paid a visit by the Scarlet Centurion, apparently somebody whom they owe a great debt too. The Centurion informs the Avengers that the five super powered beings that had shown up were the ones he said were the evil beings he foretold would come one day. He instructs the original Avengers to stay at Avengers Mansion to await further orders.
Back in the subway tunnel, Goliath considers the possibility that a device called a Herodotron might still exist. In their own timeline, Goliath helped construct this device, which would record all historical data. Figuring they have nothing to lose in checking, they go to the building on Long Island which housed the Herodotron in their own time. They break into the facility and find that it does indeed exist in this alternate reality. They decide to wire Captain America into the device because he has the will power to handle all the incoming information.
Searching through the recorded history, Captain America finds the truth: Back during the early days of the Avengers, following their battle with the Space Phantom (Back in Avengers #2) before the Hulk could leave the group they are visited by the Scarlet Centurion. The Centurion offers them knowledge of the future so that the group may conquer famine, plague, and pestilence from the world and bring on a golden era of peace. The Avengers decide to hear out the Centurion who tells them that the world's problems are the result of so many super powered beings running loose.
The Avengers then go on a mission to capture all the super-beings, starting with the Fantastic Four, then Spider-Man, the X-Men, Sub-Mariner, Dr. Strange. They prevent SHIELD from ever forming by capturing its founding members, and defeat Daredevil. With all the world's heroes captured, the Avengers then take down every super-villain in the world. Not even the combined efforts of Dr. Doom, Electro, the Mandarin, and Dr. Octopus can stop the Avengers. After all the super-powered beings on Earth were defeated by the Avengers, they then declare control of the world and order the stop of all atomic tests and scientific inquiry in an attempt to halt the advent of new super-beings.
Stopping the history play-back, Cap informs his fellow Avengers that their counterparts in this new timeline have turned the world into a dictatorship under their complete control. The group decides that the only way they can stop this reality's Avengers is by correcting the divergence they made in time. They decide the best thing to do is to recollect Dr. Doom's time machine, which they learn has been disassembled and all its parts have been spread out around the city. The Avengers split into groups to find each part.
Hawkeye and Black Panther travel to the construction site of a new office building to locate the first piece of the time machine. There they get into a battle with the Hulk and Iron Man. Hawkeye easily defeats Iron Man with