Your destiny is already mapped out as soon as you're born - you just don't get to see it yet.
In this era, people are given necklaces at birth. On these necklaces, an empty, corked bottle hangs, and as time goes by, the bottle fills with multicolored sand in a specific pattern. When you come of age, your bottle will fill entirely to the top. The real kicker is, only one other person in the whole world shares the same sand pattern as yourself, and that person is the who you are meant to be with; your soulmate, your other half, your match. Trinity Harpers, a girl who to this point, had been living a life void of interesting stories to tell, has just come of age. And her match - well, he's not exactly the Prince Charming she had in mind.
And destiny is a funny thing - it doesn't like to be messed with.