Picking up immediately where the previous season finale ended, Clarke and the surviving 48 juvenile exiles (out of the original 100) are alone in their white rooms, frantically trying to make sense of the bizarre surroundings, while the fates of Bellamy, Finn and Raven are still unknown. Outside the lab, Lincoln and Octavia's daring plan to find their friends is thwarted when a lethal enemy returns. Meanwhile, Abby, Kane and the few hundred survivors of the Ark must face physical and moral dilemmas in their dangerous and beautiful new world. Alone on the orbiting remains of the Ark, Jaha makes a heroic decision. Written by Larry B.

Clarke confronts the Underground community President Dante Wallace and demands answers. Meanwhile, Kane interrogates one of the 100 for information about the area and the Grounders, and Abby performs emergency surgery. Meanwhile, Octavia resorts to violence to find Lincoln and to who is holding him.

Clarke and Anya join forces to escape Mount Weather. Kane issues an order to have Abby brutally punished. Octavia searches for Lincoln.

After being betrayed by Anya, Clarke takes matters into her own hands. Meanwhile, Bellamy, Finn, Murphy, Sterling and Monroe race against time to save a survivor of the Ark crash, and Raven struggles to cope with her paralysis.

While Kane leads a mission to make peace with the Grounders, Jasper agrees to participate in a risky experiment, and Finn's search for Clarke takes a violent turn.

Tensions run high between Clarke and Finn, and Raven discovers that Mount Weather is interfering with Camp Jaha's communication systems. Meanwhile, Jasper and Monty discover the truth about what's going on at Mount Weather.

Clarke comes up with a new plan to stop the Grounder's attack. To fulfill that, she has to make a deal of her own. At Mt. Weather, Jasper and Monty want the truth about everything. Dr. Tsing is conducting an experiment that could change her people's lives forever, ending the 47. Everyone knows that a deal always has a price. And that price sends Clarke over the edge. Written by Alexa Montesino

Finn struggles with the aftermath of his actions, as flashbacks show his and Raven's relationship on the Ark. Meanwhile, Clarke returns to Camp Jaha with devastating news, and Abby gathers information from an unlikely source and prepares for a fight. Written by ab1995

The alliance between Camp Jaha and the Grounders is jeopardized when Gustus is poisoned. Meanwhile at Mount Weather, Monty lands himself in hot water.

Clarke and Lexa encounter a new enemy. Bellamy and Lincoln work together to break into Mount Weather. Murphy helps Jaha confront his past. Indra makes Octavia an offer she can't refuse.

Bellamy receives help from an unlikely source after being captured. Meanwhile, Abby fights to stay in control, and Jasper confronts President Wallace.

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.

Lexa plots to kill Octavia when she finds out she and Clarke knew about the missile launch. Meanwhile Jaha and his new team face a more dangerous obstacle on the desert. Bellamy uses all his effort and help from Raven and Wick to shut down the acid fog. And it's time for war as the grounders and the sky people set off to attack Mt. Weather Written by Ababio Daly (Sparkles)

Clarke and Lexa prepare for battle, while Raven and Wick experience a major setback.Octavia and Lincoln are each forced to make a difficult decision. At Mount Weather, Jasper and Maya witness a horrible act, Bellamy follows through on a promise and Cage goes public with powerful information.

After being betrayed by Lexa, Clarke makes a final stand against Mount Weather, while Jaha shocks Murphy as they continue their journey to the City of Light.