Clarke and Lexa's story continues as they battle new enemies and fight to maintain the alliance.

Lexa wants the Sky People to join the Coalition and become the 13th clan. Some like the idea, while others are weary. Clarke and Lexa come up with a perfect solution: travel the twelve clans after a meeting in Polis. It'll give them time to relax after going through so much, time to prove once again that the SkaiKru is a good ally, and time for Lexa to be among her people. Will the Sky People successfully join the Coalition? Will Clarke and Lexa ever have peace and quiet?

Clarke and Lexa have finally freed their people and gotten together, but their life is never that simple. When a new enemy arises and joins an old enemy, will their people's combined strength be enough? Or will they lose everything they love?