On a dangerous mission to gather information about his parents killer, Night walker is captured by princess Celestia. His reputation as Nightmare Blade, one of the best assassins in Equestria, leads to him being given a choice. He can either spend the rest of his life in the dungeons, or he can use his skills to help Equestria. He chooses to work for the princesses, and gathers a team of other ex-criminals to help him. These ponies fight back against Equestria's underground. They become close partners with the mane six and the princesses, and all of them learn a new things about friendship, hard choices, and love.