The 100

In the fifth season premiere, Clarke (ELIZA TAYLOR) struggles to survive on a desolate, scorched earth, while her friends in space come across a long-awaited beacon of hope.

Octavia (series star MARIE AVGEROPOULOS) is forced to take guidance from an unlikely ally when the future of the bunker and all those inside it is jeopardized.

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.

Our heroes are forced to rely on the help of Shallow Valley's dangerous new inhabitants in order to save some of their own - with surprising results.

Octavia leads her people toward 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.

Kane'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.

The growing fractures in Wonkru threaten to explode once and for all. Meanwhile, in Shadow Valley, Murphy (series star RICHARD HARMON) starts a fire, unleashing catastrophic results.

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.

As Clarke races to save Abby, she learns more about the trials and tribulations Wonkru faced in the bunker, and the impossible decisions they were forced to make in the dark year.

In part one of the fifth season finale, Octavia leads her people into war. While behind enemy lines, our heroes must overcome their differences to save Wonkru from extinction.

In part two of the fifth season finale, Clarke and her friends must risk everything to fight one last battle for survival - only to glimpse an even darker threat to the last living valley on Earth.