Video: When we last left The 100, an AI had informed Clarke that a number of power plants are leaking radiation and will destroy most of the planet. In the trailer for season four, we're seeing hints that the AI might not have been lying.
Image: Screencap from the trailer of The 100, The CW
We're also seeing everyone commit to more and more extreme actions in the name of survival, or vengeance, or "my people". Things seem, somehow, to be getting even darker.