The 100 season 3 ended on a bittersweet note, with a doomsday threat looming over Sky Crew yet again. In the season 3 finale, Clarke Griffin pulled the "kill switch" on Alie and destroyed the City of Light for good, thereby also destroying humanity's only chance of survival from an impending Nuclear apocalypse.
As it turns out all nuclear power plants have already started melting, because of a large percentage of Earth will become uninhabitable within the next six months, making Clarke's victory short lived. The finale also reunited all the Sky Crew as the effect of Alie's chip faded away. Also, Octavia drove a dagger through Pike's heart, thereby seeking vengeance for Lincoln.
Marie Avgeropoulos, who plays Octavia Blake in the show spoke to E Online about season 4 return date and teased a dark turn for her character. She said, "Octavia is going to get darker next season. There's a lot of twists and turns coming up for season 4, which is going to air next year between January and March."
Furthermore, The 100 is missing from The CW's fall show list, which implies, that the show will not return for its fourth season in 2017.
Isaiah Washington also spoke about his character's [Jaha] redemption in season 4, given the fact that he is the one who brought Alie to Arkadia. "There's going to be a lot of roads of repair for Jaha's character. It's going to be interesting to see [what] the writers come with to hopefully get him somewhere because you'll see after [the finale] he takes a pretty hard fall. He's got a lot of 'explaining to do," Washington shared.
Meanwhile, the plot for The 100 season 4 will be about Clake's decision in season 3, and how the people of Arkadia will survive the second Nuclear meltdown. Moreover, according to an Entertainment Weekly report, Luna will return in The 100 season 4. Eliza Taylor told EW, "Personally, I would love to see her come back. Nadia [Hilker] is such a beautiful, intriguing actress, and Luna is such a great character. There's a lot more we could do with her for sure."
The 100 writers have also teased a theme for season 4 via Instagram. In one of the images posted on the picture sharing site, they teased, "Save The World." While the second image was captioned, "Goes badly."