It is 15 years after Harry Potter destroyed the Dark Lord, and since then, the magical world has been at peace.  A few days ago, in America, Something happened to change that.  The Muggle President was about to announce the existence of  magical creatures, and that the world had nothing to fear.  The Ministry of Magic, and most other Magical forms of government even agreed that it would be best to let the muggles know they were here.  But some people didn't agree.
Just after the announcement, a person teleported behind his and murdered him.  They announced in disguised voice that the muggles would fall to the might of Magic, then left to commit numerous terrorist acts around the country and the world.
As a result of the mass hysteria that resulted, the muggles demanded that the threat presented by witches and wizards be contained.  The new President ordered the military to storm area 51, the US center of magical activity, like Diagon Alley, the ministry, and a housing district rolled into one.  There they rounded up and imprisoned everyone they could catch.
The next day, martial law was declared and the Magical Containment Division (MCD) was formed.  Using spy satellites to track down magic witches and wizards to within a few hundred feet, and hand scanners to lock onto specific people, they track down anyone who surfaces.  The witches and wizards of the world have went into hiding, most deep underground where the muggle's magic detection devices can't find them.

I have only seen the movies, so I don't know a lot about it, but here's the basics.  I'll be playing as a young man that didn't find out he was a wizard until they came for him, so I won't be in charge of the underground camp.