Discovering that Jasper may still be alive, Clarke, Bellamy, Finn, Wells and Murphy head out to find him. On the Ark, Abby is determined to prove Earth is habitable, and enlists a mechanic to craft an escape pod.

As a dangerous, acidic fog approaches, Clarke, Finn and Wells set out in search of a seaweed-like plant to make an antibiotic poultice for Jasper's wounds, while a vulnerable young girl follows when Bellamy takes a group out hunting for food.

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.

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 is still on her own in the white room, frantically attempting to make sense of her bizarre surroundings. Lincoln and Octavia's plan is ruined and an enemy returns.

After discovering a horrifying project in Mount Weather's medical ward, Clarke joins forces with an unexpected ally.

Lives are left in danger following the arrival of a new threat. Lincoln and Bellamy decide to break into Mount Weather.

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.

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

Three months have passed since the tragedy at Mount Weather and our heroes learn that a bounty has been put on Clarke’s head. Unbeknownst to Clarke, a team led by Bellamy and Kane journeys deep into Grounder territory to save her. Meanwhile, Murphy finds his way to the mansion and discovers a very different Jaha on a very different mission.

Clarke is torn between vengeance and mercy. Meanwhile, Kane and Octavia work together to avert a disaster, and Abby continues to worry about Raven.

Lexa tries to maintain peace and order within the clans, and Clarke uncovers a strange and game-changing truth. Meanwhile, a flashback takes us into the darker chapter of humanity’s past.

Clarke is on a mission that could change everything. Meanwhile, Murphy gains insight that might prove useful in ensuring his survival. Lastly, Kane reaches a breaking point.

Our heroes begin to face the reality of their tragic situation. Everyone prepares for a final showdown.

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

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

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

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.

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

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.

Clarke tries to win over the leaders of Sanctum in order to let her people stay. Meanwhile, Bellamy, Echo and Octavia discover a new threat while on a mission to retrieve the transport ship.

Echo and Gabriel learn more about Hope and her mysterious past.