In which Loki is NOT invading Midgard, thank you very much

AU during The Avengers (2012).
'Loki' has been captured in Germany and Thor has been despatched to Earth to deal with him, but what if it wasn't really Loki?
While arguing in front of the sceptre and unaware they're all being influenced by it, no one is prepared when Loki shows up in the lab and claims to NOT be leading an invasion, and that someone is framing him.
With more understanding of magic on their side than Thor can provide, what will come to light about the imposters actions and the truth of the invasion?
What will happen when the real Loki gets involved, and has exactly no time for the pettiness of mortals when there is an impending invasion? How will the Battle of New York go with another player added to the mix?
And should the public be told what has been going on? SHIELD don't think so, but SHIELD aren't calling the shots anymore.
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"Why would you come?" Thor demanded.
"Why do you think, you imbecile? I want to know who is attacking Midgard, and, more importantly, why they are using MY face to do it."