After arriving on a new planet, our heroes found a place where they hoped to try again. Clarke and Bellamy led a group down to this mysterious world to start anew, but not everything on Sanctum was as perfect as it seemed. Despite their determination to do better, threats both seen and unseen once again forced them to fight for their lives and the future of humanity.

For four seasons, The 100 have fought to survive. That fight has torn them apart, turned them against each other, and taken the lives of their closest friends. Season Four introduced our heroes to the harsh truth that the human race is doomed to face an unbeatable enemy: the remaining nuclear reactors on Earth have melted down and are setting the atmosphere on fire. Our heroes had very little time to prepare for the worst, with every possible solution disappearing almost as quickly as they were able to come up with them. With a literal countdown to the end of the world, our heroes will be forced to go to unimaginable lengths to make it out alive – with or without each other. In the aftermath of Praimfaya, they must begin again, and with Season Five our heroes will have to examine their responsibility to the new place they call home, and the future generations who will inhabit it. Can they begin again and celebrate what remains, or will the frailties of human nature cost them their one chance to rise from the ashes?

The fourth season picks up right where we left off. Clarke has just learned the human race is doomed to face an unbeatable enemy. Alie was telling the truth. The remaining nuclear reactors on Earth are melting and will set the atmosphere on fire. Can our heroes find hope knowing the end is inevitable? Will they spend their remaining days trying to survive? Or will they use their limited time to finally live? The stakes have never been higher, alliances are breaking, and the world is about to collapse. Civility has no place at the end of the world and there's no telling what lengths our heroes can and will go to in order to survive.

In the third season, an artificial intelligence named A.L.I.E. is revealed to be responsible for the nuclear apocalypse that devastated Earth 97 years before the series, and she has a secret agenda of her own. Camp Jaha, now renamed Arkadia, comes under new management when Pike, a former teacher and mentor, was elected over Kane as Chancellor and begins a war with the grounders.

The second season picks up with the group still scattered and desperate to be reunited. As members of The 100 and new arrivals from the Ark stake out their place in a dangerous and beautiful new world, they are confronted with the physical peril and moral dilemmas that come with reforging a society.

Set 97 years after a nuclear war has destroyed civilization, when a spaceship housing humanity's lone survivors sends 100 juvenile delinquents back to Earth in hopes of possibly re-populating the planet.