Octavia fights in the final battle for her people's survival, but not everyone is willing to play fair.

It's a race against the end of the world as Praimfaya arrives forcing our heroes to make impossible decisions to ensure their survival.

Jaha and Kane disagree over how to handle their grim reality. Meanwhile, Clarke leads a group to save a friend.

Clarke makes a desperate plea with a former allied force in an attempt to avoid a war and ensure the survival of her people.

Clarke faces the consequences of her fateful choice.

Continued struggles with leadership and trust in Arkadia and Polis take violent turns while Abby leads a team to a distant location hoping to find answers.

After a disappointing discovery, Clarke and Abby question how far they're willing to go. Meanwhile, Jaha finds a lead to the mysterious Second Dawn.

Jasper and Bellamy go on a quest. Meanwhile, Clarke struggles to keep the peace after word of Jaha's discovery spreads.

Jaha leads Clarke and Bellamy down a road to possible salvation while tensions rise in Arkadia and Polis.

Clarke and Roan are forced to work together when they are tasked to deliver a dangerous but crucial asset to Abby through enemy territories.

Clarke's arrival on the island quickly takes a turn for the worse. Meanwhile, Bellamy tries to avoid further tragedy in Arkadia.

Clarke and her friends struggle with how to proceed after the fate of the world is revealed.

The burden of leading weighs heavily upon Clarke and Bellamy when different challenges force them to determine who will live and die.