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.

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

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

Clarke ends up being betrayed by somebody that she trusted. Bellamy, Finn and Murphy attempt to save a stranger.

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.

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.

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

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.

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.

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