Set after 3x7, Clarke thinks Lexa is dead, and spends the next year in a tumble of severe depression, little does she know that Lexa is alive, and is making her way back to her true love.
Basically what should have happened :)
What would happen if Lexa survived the gun shot? What if Clarke saved her? This is clexas struggle to be together and lead both their people to peace. They won't fight their love anymore, only let themselves be stronger because of it.