(For those of you who haven't finished A New Equestria, this story will contain spoilers. Some major, some minor.)
Rainbow Dash the element of loyalty, councilpony in the New World, and close friend of both Applejack and Princess Twilight Sparkle, finds herself an outcast. By all means she is a criminal that broke out of jail. And so, she sets out to redeem her name and find a user of illegal magic, with the help of the organization called Umbra Equestria.
An organization that she now leads.

Thirteen years have passed since the madman that framed Rainbow Dash had been apprehended, and Umbra has flourished. Now a massive organization that has branches across all of the known world, Umbra Equestria has become one of the greatest secret police organizations in the known world. All, with Rainbow Dash as it's head.
(Takes place in a technologically advanced Equestria, think the Anime GitS:SAC for a reference.)
(cover image found off of google.)