The life of a well known assassin becomes chaotic when he finds he purchased the daughter of an old rival at a slave market, leaving him the choice to give her back to spare himself or keep her and die.
Being specific is your friend. Turning a world upside down isn’t a story. It can be used for nearly anything and that is the problem.
How is his world turned upside down. Is he now being pursued? Is he in love with her, when he should kill her for revenge?
Give us a goal, action, obstacle combination.