Summary:

Captain America is back from the dead, and all should be well. Too bad the world didn't stop and wait for Steve's return and no one ever gave him a chance to get used to the latest changes in the team dynamics. And it would really help if things between him and Tony weren't quite as raw - and if both of them weren't so spectacularly bad at talking to each other.

Also, there's a threat for the existance of mankind. But no one but Tony actually cares about that.