A Princess is 'of that age', and has two suitors. Prince Charming is her favourite, for he is tall blonde(ish) and handsome, with a promising career in IT. The Duke of Doon is the King's favourite, because despite having some flaky degree in social science, when in the presence of the King or Queen, he sucks up more than a catwalk model at a party.
One day, the King invites both suitors and the beautiful Princess, to his country residence. Whilst standing on the driveway, a sort of gravel arrangement made of black and white pebbles, he thinks of a way to solve his dilemma. He explains that he's going to put one black stone, and one white stone into a bag. He'll then ask his daughter to select a stone without looking into the bag. Which ever stone she picks will decide which suitor will marry her.
That old snake in the grass, the Duke of Doon, offers to be represented by a black stone. He goes on to offer to select the stones and prepare the bag. The King naturally agrees to his offer. However, the sharp-eyed Princess notices he puts two black stones into the bag. Oh no! That means Prince Charming cannot possibly win the challenge!
How can the Princess evade the Duke's dastardly plan?