Clarke and her friends must risk everything to fight one last battle for survival, only to glimpse an even darker threat to the last living valley on Earth.

Jaha makes a surprising move. Clarke gets help from an unexpected source. Lincoln seeks revenge.

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.

Clarke confronts a new adversary. A surprising connection takes us back to the past and to the nuclear apocalypse that destroyed the Earth.

As the remaining members of the 100 face off against the Grounders, Jaha makes a noble sacrifice to ensure the Ark makes it to Earth.

Clarke comes back to Camp Jaha with some shocking news. Finn has to face the consequences of his actions.

Bellamy leads the charge investigating a potential way home. Meanwhile, Clarke and Madi deal with the new, uncertain threat to their home.

Lexa and Clarke get into a heated discussion during battle preparations; Bellamy races against time.

Wick and Raven are faced with a setback. Maya and Jasper witness a terrible act.

Octavia leads her people into war. While behind enemy lines, our heroes must overcome their differences to save Wonkru from extinction.

Lincoln and Bellamy's efforts to get into Mount Weather has some brutal consequences.

Clarke wrestles with a decision. Bellamy learns that something isn't what it seems. Meanwhile, Murphy plots to betray his former Chancellor.

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

Octavia is forced to take guidance from an unlikely ally when the future of the bunker and all those inside it is jeopardized.

Clarke begins to question Lexa's leadership decisions and Indra continues to push Octavia. Meanwhile, at Mount Weather, Jasper steps up into the role of leader, and Cage throws Maya into a life threatening situation.

Clarke struggles to survive on a desolate, scorched earth while her friends in space come across a long-awaited beacon of hope.

Jordan investigates Sanctum. Meanwhile, Octavia and Diyoza discover the threats of the new planet firsthand. Lastly, Bellamy and Clarke butt heads.

A special Naming Day changes everything in Sanctum. Gabriel comes face to face with an old friend.

Bellamy is able to get Clarke to agree to accompany him to the drop ship. Dr. Tsing is in charge of a deadly experiment.

Clarke is faced with a difficult choice and Raven helps Bellamy navigate Mount Weather as Dr. Tsing begins to harvest the 47, while Jaha and Murphy encounter a stranger on their journey to the City of Light.

Clarke discovers the mastermind behind a devious plan. Kane struggles to keep the peace. Meanwhile, Jasper’s grief drives him to reckless behavior.

Our Heroes are forced to rely on the help of Shallow Valley's dangerous new inhabitants in order to save some of their own, with surprising results.

The growing fractures in Wonkru threaten to explode once and for all. Meanwhile, in Shadow Valley, Murphy starts a fire, unleashing catastrophic results.

Clarke and Finn come face to face with a new enemy after Lincoln rescues them from Anya, while Bellamy, Raven, Octavia and Jasper deal with a vengeful Murphy. On the Ark, Jaha makes a plan to try and get to Earth.