Revised Version
Infiltrators, they are the first wave in any Changeling invasion. They impersonate a pony in places found with abundances of love. But some are given different a type of mission. Assassination. They will continue until completion or death. With Queen Chrysalis continuing to harbor a grudge against Twilight and her friends for ruining her invasion of Equestria, she sends an infiltrator to end Twilight. But, what happens when the changeling does not wish to take a life. But Chrysalis is nothing if not a master manipulator.
1/19/17 On Hiatus for revision
6/22/17 Revisions much larger than I originally expected. Starting a total rewrite and posting it as a different story under the same name. I'll try to keep as much of the original idea in the reboot.