It's apocalypse now — again — for humankind on season 4 of "The 100."

Last season ended with artificial intelligence Alie warning Clarke (Eliza Taylor) that the planet's remaining power plants are melting down — and about to cause nuclear annihilation. In the first trailer, Clarke is desperately trying to rally her people and the Grounders to work together to save the world.

I know you're afraid. I know you're angry. But if we stick together, we won't just survive. We'll thrive," she promises.

But old wounds run deep among Skaikru and Grounders, and it's going to take strong leadership on Clarke's part to heal those wounds.

Nobody seems to be in a particularly happy place. Jaha (Isaiah Washington) must grapple with his actions in allowing Alie to turn everyone into zombies. Octavia (Marie Avgeropoulos) is raining "death from above" in vengeance for her dead lover, Lincoln. And Monty (Christopher Larkin) is questioning Clarke's actions. At least it looks like Kane (Henry Ian Cusick) and Abby (Paige Turco) kiss!

"The 100" season 4 premieres February 1.

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