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.

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.

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

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

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

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

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

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.

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

Clarke finds hope in the most unlikely place. Meanwhile, Alie’s master plan comes together.

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

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

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

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

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

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 discovers a shocking truth, and Octavia is forced to make a decision that could have devastating consequences. Meanwhile, Kane and Abby share a moment.

Clarke, Bellamy, Octavia and Jasper hit a tragic roadblock. Meanwhile, Raven and Monty make an important discovery.

Clarke wants answers from the President. Abby performs emergency surgery. Octavia will do anything to find Lincoln.

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

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.

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

Alie forces Raven’s dark side to come out, and Jasper’s anger continues to grow. Meanwhile, Octavia wrestles with her place in the world, and Monty is forced to make a split second decision.

Jaha employs a terrifying new method to convince Abby to join his cause, Kane is on a mission, and Bellamy is hit with a hard truth. Meanwhile, Monty finds himself in a precarious situation, and Jasper rushes to save one of his own.

Kane takes part in a mission to make peace with the Grounders. Jasper decides to take part in a risky experiment. Lincoln enters a world of pain and President Dante Wallace issues a warning.

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.

Tensions are running high between Clarke and Finn. Raven finds out that Mount Weather is interfering with their communication systems.

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.

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.

Raven faces an unexpected threat. Clarke must keep the peace among opposing factions in Sanctum.

Clarke and her friends attempt to rebuild Sanctum as a new threat rises in the woods.

The red sun derails Clarke's plans.

97 years after a nuclear war, human kind is living in space. 100 juvenile delinquents are sent down to Earth to see if the planet is habitable.

Clarke and her friends reckon with all that has happened only to find an unexpected threat looming.

Clarke and her friends find themselves on a planet that is not what it seems.

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.

Emori tries to heal Sanctum's old familial wounds while Echo, Octavia and Diyoza struggle with new ones.

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

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.

Where in the universe is Bellamy Blake?

It's a new day in Sanctum. Clarke, Octavia, Raven and Echo struggle with a new foe.

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.

Bellamy, Clarke and Finn try to protect Charlotte when everyone learns she killed Wells. On the Ark, Abby risks getting floated in order to give Raven the chance to launch the escape pod.

Mysterious outsiders arrive with news of Clarke's missing people.

Clarke and Octavia mount a desperate rescue mission as the Disciples close in on what they want.

Monty strives to show Wonkru an alternative to war, and to the valley itself. Meanwhile, Abby’s health continues to deteriorate, along with McCreary’s patience.

Murphy and Indra must defuse a tense situation. Old friends make new allegiances.

After all the fighting and loss, Clarke and her friends have reached the final battle. But is humanity worthy of something greater?

Octavia and Diyoza make their way to the mysterious anomaly in search of the Old Man. Meanwhile, Murphy has an offer for Emori.

Octavia gets to know a whole new world. Meanwhile, Murphy and Emori play make believe.

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

The team on the ground flights to survive the threat they face on the new planet. Meanwhile, Raven must join forces with an unlikely ally to save everyone on board the Mothership.

Diyoza learns more about the mysterious Children of Gabriel while Abby continues searching for a way to save Kane.

Clarke and Finn are captured by Anya, who forces them to save the life of a victim of the explosion. Meanwhile, Raven deals with her split from Finn, and Kane fights to save the Ark and it's survivors.

Shumway secretly orders one of the 100 to kill Bellamy. Meanwhile, hallucinogenic nuts provide Octavia with an opportunity to help the Grounder escape the camp, and Bellamy and Clarke investigate a nearby underground depot, where they find military weapons.

Bellamy, Finn and Jasper head into Grounder territory to search for Octavia, as flashbacks show the siblings' difficult childhood on the Ark. Meanwhile, Raven finds out about Clarke and Finn.

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

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.

Clarke’s past catches up to her.