A king's word is law, but what if that word changes your life, and not for the better? Prince Gumball dictates Fionna is of age and must marry, and that he shall chose her husband. But Fionna does not want to marry some stranger. Change is never easy, especially when things don't turn in your favor. Good thing she knows a certain scheming, Gumball-hating Vampire King.

When Marshall Lee's title as Vampire King is threatened, Fionna finds herself thrown into a world of intricate plots and vampire politics. Fionna knows nothing about vampires except that they're rarely good. But Marshall Lee is… right?