Bellamy and Lincoln's attempt to sneak into Mount Weather has brutal consequences. Abby fights to stay in control as Clarke steps up in her new leadership role. Meanwhile, with Monty and Harper (co-star Chelsey Reist) still missing, a desperate Jasper confronts President Wallace and demands answers.

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.

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

Alie (recurring guest star Erica Cerra) forces Raven's dark side to come out, while 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.

While Abby leads a team to a distant location, hoping to find answers, the continued struggles with leadership and trust in Arkadia and Polis take a violent turn.

Clarke's arrival on the island takes a turn for the worse; Bellamy tries to avoid further tragedy in Arkadia.

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.

In the season finale, it’s a race against the end of the world as Praimfaya arrives, forcing our heroes to make impossible choices to ensure their survival.

Bellamy (series star BOB MORLEY) leads the charge investigating a potential way home. Meanwhile, Clarke and Madi (recurring guest star LOLA FLANERY) deal with the new uncertain threat to their home.

Octavia leads her people towards Shallow Valley against the advice of Clarke and Bellamy. Meanwhile Kane (series star HENRY IAN CUSICK) and Abby (series star PAIGE TURCO) adjust to a new set of challenges.

Kanes's attempt to prove himself useful tests Wonkru's allegiance to Octavia. Madi faces an unexpected threat inside Wonkru, forcing Clarke to make an unlikely ally.

Clarke and Bellamy make a startling discovery about Wonkru’s battle plans as Echo (new series regular TASYA TELES) risks her friendship with Raven (series star LINDSEY MORGAN) to complete her mission.

Clarke’s determination to protect Madi puts Bellamy in an impossible situation.

Monty (series star CHRISTOPHER LARKIN) 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. Series star Henry Ian Cusick directs.