10. The Trigger Event For The Twins
It looks like there are going to be multiple time periods explored in the film: the very beginnings of the "dormant" security programme will presumably focus on the early days of SHIELD (though the suggestion that Cap actually time travels feels a little hokey), and of course the modern setting will take up where Captain America 2 left off. But then there's another time period, which will presumably look back to how Scarlett Witch and Quicksilver end up being taken captive by Baron Von Strucker's forces. There are clearly shots in both trailers of an Eastern European setting - Sokovia no doubt - some time in the fairly recent past (the cars are a dead giveaway), suggesting that it's a flashback sequence. And of course this has to be the key to why the young newcomers align themselves with Ultron against the Avengers initially. Presumably the Twins' escape to back to Sokovia prompts the use of the security drones that go rogue and prompt a rescue led by Clint Barton: they're deemed large enough threats having already bested the Avengers once after all. And perhaps that's how they initially come into contact with Ultron, who later returns to use their powers against the Avengers. And it won't just be the "mutants" whose past is explored by the look of the second trailer...