In a desperate attempt to treat Jasper’s festering wounds, Clarke, Finn and Wells set out in search of a seaweed antibiotic. Bellamy and his crew go hunting for food, and are joined by Charlotte, a lovable 13-year-old, who feels safe under Bellamy’s protection. A thick, acidic fog appears, forcing Clarke, Finn and Wells to seek shelter inside an ancient van. While they are trapped, Clarke confronts Wells on his betrayal that resulted in her father’s death.

The episode was rated 7.57 from 5126 votes.

After the shocking death of one of their own, Clarke and Finn grow closer as they try to figure out a way to communicate with the Ark. Bellamy must keep the group from turning on one another as life on Earth takes a desperate turn. Meanwhile, Abby risks having herself floated in order to give Raven the chance to stow-away in the escape pod bound for Earth.

The episode was rated 7.57 from 4721 votes.

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

The episode was rated 7.53 from 557 votes.

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.

The episode was rated 7.53 from 5501 votes.

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

The episode was rated 7.50 from 12 votes.

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

The episode was rated 7.50 from 713 votes.

Having discovered that Jasper may still be alive, Clarke, Bellamy, Octavia, Finn and Monty set out on a mission to locate their friend and are shocked at what they find. Meanwhile, on the Ark, Abby is determined to get to Earth, and enlists Raven to craft an escape pod.

The episode was rated 7.45 from 5560 votes.

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

The episode was rated 7.45 from 1067 votes.

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

The episode was rated 7.36 from 852 votes.

Ninety-seven years ago, nuclear Armageddon decimated planet Earth, destroying civilization. The only survivors were the 400 inhabitants of 12 international space stations that were in orbit at the time. Three generations have been born in space, the survivors now number 4,000, and resources are running out on their dying "Ark." Among the 100 young exiles are Clarke, the bright teenage daughter of the Ark’s chief medical officer; the daredevil Finn; the brother/sister duo of Bellamy and Octavia, whose illegal sibling status has always led them to flaunt the rules, the lighthearted Jasper and the resourceful Monty. Technologically blind to what’s happening on the planet below them, the Ark’s leaders — Clarke’s widowed mother, Abby; Chancellor Jaha; and his shadowy second in command, Kane — are faced with difficult decisions about life, death and the continued existence of the human race.

The episode was rated 7.36 from 6813 votes.