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.

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

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 manage to make a deal.The newly created alliance is under threat. Monty comes up with a plan.

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

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 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.

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.

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 returns to Polis, and Murphy has a surprise encounter. Meanwhile, Octavia uncovers a clue.

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.