Chrysalis assign a special changeling a mission, but soon later that changeling begins rethink of his actions. He then to cuts off with his queen for some reason, and the queen was not to happy about it. Nopony that's a changeling of course knows that he is a changeling. So now he has the changeling army after him and anypony that might figure out that he is a changeling.
Allow me to fill the void of the comments section.
Stop saying "changeling".