The season finale of the The 100's third go-round left Clarke Griffin dealing with a lot on her plate, like going into the City of Light, confronting A.L.I.E., gaining the knowlege of past Commanders, and saving the world from AI, but she learned that a greater threat is on the horizon. There are six months before the Earth is ravaged once again by a nuclear holocaust, but time can be stretched in television, so don't let that lead you to believe that the end of the series is in sight, especially since Season 4 picks up right where the Season 3 finale left off, with what series creator Jason Rothenberg promises will be a big opening scene.
At Comic-Con, the cast and crew confirmed more details for Season 4, including the return of Luna, that Octavia will go looking for Indra and that her murder of Pike only ignites more darkness, and that Roan (Zach McGowan) is a series regular. Grounders are looking for Nightbloods, clean water will be a major problem, and the Flame is still present. Clarke won't be in a rush to replace her broken heart after Lexa's death, but she has more pressing needs, like finding out how to save the world – yet again. Will she tell the others about the radiation? Or will she allow people to live out their lives and enjoy it? Also, the Season 4 theme will be not only can they survive, but also whether the remaining humans deserve to survive.
The Earth, itself, is the big, looming villain in Season 4, and I spoke to The 100 showrunner Jason Rothenberg and cast members Eliza Taylor (Clarke Griffin), Marie Avgeropoulos (Octavia Blake), Richard Harmon (John Henry), Henry Ian Cusick (Marcus Kane) and Christopher Larkin (Monty Green), who each shed some light on some key elements to look forward to when the series picks back up in early 2017.