Right before Clarke Griffin's 18th birthday, she travels to Polis to marry a boy. Clarke was finally getting used to the idea of marrying him when his older sister started to cause problems in more ways than one.
Book 1 of the Praimfaya Series - Clarke and Lexa survive praimfaya and have to survive six years being alone. They aren't as alone as they think though. Their food starts being stolen and get injured from traps. One day, something changes.