In the fourth season, Clarke attempts to save as many people as she can from the coming death wave as predicted by A.L.I.E. and confirmed by Raven Reyes. As part of this, Clarke allows herself to be the recipient of a bone marrow transplant as a test subject to see if Nightblood can be recreated. However, her mother stops the testing, fearing for Clarke's life and she is left unsure if she can survive the coming radiation or not. With 1,200 survivors in a massive fallout bunker, Clarke and several of her friends attempt to escape to the remains of the Ark in space as an alternate means of survival. Clarke remains behind to power up the Ark remotely, missing her chance to escape as the death wave arrives. Six years later, Clarke's Nightblood is revealed to have saved her from the death wave and she has adopted a young Nightblood named Madi, the only other survivor Clarke could find on the planet. As Clarke continues to attempt to communicate with her friends without success from Shallow Valley, the only inhabitable part of Earth left, a prison transport ship arrives.
