It's AU (medieval I believe), Odin died and Thor is King (though not rigthfully so) he sends his brother to Tonys (Anthonys?) Kingdom to marry him/become engaged.
Loki thinks at first that all people in Tonys Kingdom are unciviliced etc... King Tony sees that Loki is not willingly there an does everything to make him feel better.
They do not know each others language and need an interpreter at first. They fall for each other...
Also later we learn that Thor actually sent Loki to spy on Tonys Kingdom.
I know it's probably not much to go by... but I hope very dearly that one of can help me.