Ninety-seven years after a devastating nuclear apocalypse wipes out most human life on Earth, thousands of people now live in a space station orbiting Earth, which they call the Ark. Three generations have been born in space, but when life-support systems on the Ark begin to fail, one hundred juvenile detainees are sent to Earth in a last attempt to determine whether it is habitable, or at least save resources for the remaining residents of the Ark. They discover that some survived the apocalypse: the Grounders, who live in clans locked in a power struggle; the Reapers, another group of grounders who have been turned into cannibals by the Mountain Men; and the Mountain Men, who live in Mount Weather, descended from those who locked themselves away before the apocalypse. Under the leadership of Clarke and Bellamy, the juveniles attempt to survive the harsh surface conditions, battle hostile grounders and establish communication with the Ark.

In the second season, forty-eight of the remaining detainees are captured and taken to Mount Weather by the Mountain Men. These are transfusing blood from imprisoned grounders as an anti-radiation treatment as their bodies have not adapted to deal with the remaining radiation on Earth. Medical tests of the forty-eight show their bone marrow will allow the Mountain Men to survive outside containment, so they begin taking the youths' bone marrow. Meanwhile, the inhabitants of the Ark have crash-landed various stations on Earth and begin an alliance with the grounders to save both their people, naming the main settlement at Alpha Station "Camp Jaha". The season ends with the massacre of the Mountain Men to save the prisoners. During this time, former Chancellor Jaha leads a group in search of a fabled "City of Light". Jaha discovers an artificial intelligence named A.L.I.E. while John Murphy finds an alarming video implying a connection between the AI and the destruction of the world.

In the third season, Alpha Station renamed Arkadia, comes under new management when Pike, a former teacher, and mentor on the Ark, is elected as chancellor and begins a war with the grounders. Pike kills an encampment of grounder warriors while they sleep, which further damages their already fragile relationship with the grounders. Furthermore, the grounder commander Lexa is killed by her mentor during a failed assassination attempt on Clarke, with whom she was romantically involved. A.L.I.E. – who was commanded to make life better for mankind – is revealed to have responded to the problem of human overpopulation by launching the nuclear apocalypse that devastated Earth, and begins to use ingestible computer chips to take control of peoples' minds. A.L.I.E. is ultimately destroyed by Clarke, but not before warning of another impending apocalyptic disaster.

In the fourth season, two dozen nuclear reactors around the world are melting down due to decades of neglect that will result in the majority of the planet becoming uninhabitable. Clarke and the others search for ways to survive the coming wave of radiation. When it is discovered that the grounders with black blood – known as the Nightbloods – can metabolize radiation, Clarke and the others attempt to recreate the formula, but fail to test it. An old bunker is discovered that can protect 1,200 people for over five years from the new apocalypse; each of the twelve clans selects a hundred people to stay in the bunker. A small group decides to return to space and attempt to survive in the remnants of the Ark. Clarke, who is now a nightblood, remains on the Earth's surface alone.

In the fifth season, six years after the meltdown of the nuclear reactors, a prisoner transport ship arrives in the only green spot left on Earth, where Clarke has been living with Madi, a young Nightblood grounder who also survived the wave of radiation that swept the planet after the meltdown. Those who survived in space and in the bunker have returned safely on the ground. A struggle for the Shallow Valley between the prisoners and a new, united clan, known as Wonkru, begins, resulting in a battle ending with the valley being destroyed. The survivors escape to space and go into cryosleep while they wait for the Earth to recover. However, Monty believes that Earth will apparently never recover and, before dying of old age, sets the prison ship on a course for a new world.

In the sixth season, after 125 years in cryosleep, Clarke, Bellamy, and the others wake up to find out that they are no longer orbiting Earth and have been brought to a new habitable world, Alpha, also known as Sanctum. After landing on this world, they discover a new society, led by ruling families known as the Primes. They also discover new dangers in this new world, and a mysterious rebel group, known as the Children of Gabriel as well as a mysterious Anomaly. Clarke falls victim to the Primes and ends up in a battle with one for control of her body, a fight which she ultimately wins. The season ends with the deaths of most of the Primes, but also with the loss of Abby Griffin and Marcus Kane. Throughout the season, Madi is haunted through the Flame AI by the spirit of the Dark Commander, an evil grounder leader that had ruled when Indra was a child. In order to save Madi, Raven is forced to destroy the Flame, but the Dark Commander escapes.

The seventh season finds the inhabitants of Sanctum trying to find a way to live together in peace following the aftermath of the events of the previous season while battling the resurrected Dark Commander. At the same time, Clarke and others come into conflict with the mysterious Disciples, humans from another world who are convinced that Clarke holds the key to winning the last war that is coming. The season also explores the mysterious Anomaly introduced in the sixth season, now identified as a wormhole linking six planets, one of them being a regenerated Earth, together. After vanishing and being believed dead for some time, Bellamy returns but converts to the Disciple cause, having gone through a life-changing experience while stuck in the cold and treacherous mountains. After returning and converting to the Disciple cause, this leads to his death at Clarke's hands. At the end of the series, the Dark Commander is permanently killed by Indra and humanity achieves Transcendence aside from Clarke who committed murder during the test. They find out the test isn't an actual war, but a way to join the alien hive mind, which is a peaceful universal consciousness that grants immortality. Clarke returns to Earth where her surviving friends and Octavia's new boyfriend Levitt choose to join her to live out their lives, so that Clarke will not be alone. They will not have children, due to their infertility and sterility, and the series ends with Clarke's group being the last humans to ever live on the mortal plane of existence, on a pristine Earth, which is now habitable again.

The 100

The series is set three generations after a thermonuclear apocalypse, wherein the only known survivors of the human race live in a space colony consisting of satellites joined together in orbit around the Earth and governed by The Chancellor, who leads its legislative council. Resources are so scarce that all crimes, no matter how small, are punishable by death, unless the perpetrator is under 18 years of age.

The 100 begins with Clarke Griffin, a former medical student, being arrested for a crime committed by her parents: conducting illegal experiments on children under threat of the corrupt Vice Chancellor Rhodes. Clarke confides in her best friend Wells Jaha, The Chancellor's son. Despite swearing secrecy to Clarke, Wells tells his father, hoping to save the Griffins from Rhodes. His plan backfires, the Griffins are arrested, and his relationship with Clarke disintegrates. Two years later, the Colony decides to send 100 of its teenage prisoners to investigate whether or not Earth is habitable. Among the 100 are Clarke, Wells, Octavia Blake, her older maternal half-brother Bellamy Blake, and Clarke's friend, Thalia.

The group crashes somewhere on the East Coast in the former United States. Once there, the 100 struggle to survive in a world very different from the past Earth. Clarke tends to the wounded, and Bellamy gradually develops a romantic interest in her. It is revealed that Octavia had become a drug addict while in prison. A few days later, someone sets fire to the camp, killing Thalia. As the survivors investigate, they discover a farm not too far from the site, leading them to the realization that they are not alone.

The 100: Day 21

Twenty-one days after they land on Earth, the 100 continue to face recurring attacks from an unknown enemy. Octavia has been missing since the fire. Wells tries to maintain morale, while Bellamy tries to find his sister. The 100 find an Earthborn girl, Sasha Walgrove, and hold her hostage. Sasha tells them that they have landed in the former state of Virginia, and that there are people from the Colony who arrived before the 100. Bellamy believes that Sasha's people are responsible for Octavia's disappearance and demands that Sasha reveal their location. Wells and Sasha bond, and Sasha helps Wells find food for the surviving colonists.

In space, the people of the Colony fight to get into their drop ships as the space station's life support begins to fail; Clarke and Wells' friends, Glass and Luke, are among the people desperately trying to get to Earth. However, they find themselves at the mercy of Vice Chancellor Rhodes, who is willing to kill to get into one of the dropships.

Sasha leads Clarke and Bellamy to a colony beneath the ruins of Mount Weather Emergency Operations Center. There, they meet her father, Max Walgrove, who is the leader of the colony. Octavia is at Mount Weather, having been rescued by Max and his people from a group of renegades. These renegades are responsible for the attacks on the 100. Max and his people will continue helping the 100, and will provide further support once the rest of the Colony arrives. At this point, they find dropships from the Colony falling from the sky.

Wells eventually realizes that there is something familiar about Bellamy and Octavia; ultimately, he discovers that their mother was Melinda Blake, the woman his father had loved before marrying Wells' mother for the sake of his career. This discovery leads Wells and Bellamy to realize that they are paternal half-brothers.

The 100: Homecoming

After the dropships crash, Clarke, Bellamy, and Wells lead a rescue party to the crash site, allowing Clarke and Wells to reunite with Glass and Luke. Clarke ponders leaving the camp to search for her parents. The Chancellor, still in a coma, remains trapped in the Colony above Earth. Vice Chancellor Rhodes takes control over the community on Earth, planning to force Luke to execute Bellamy, as a warning to anyone attempting to challenge him.

With Sasha's help, Clarke and Wells escape with the wounded Bellamy. In addition, Glass and Luke flee the camp to escape Vice Chancellor Rhodes. One of Rhodes' men kills Sasha when she tries to get more supplies. Rhodes plans to attack Mount Weather to recapture Bellamy, Clarke, and Wells. As Mount Weather prepares for Rhodes' attack, some of the Colonists revolt and join their benefactors against Rhodes. Clarke, Bellamy, and Wells are captured during the initial exchange, but another faction of Earthborns defeat and capture Rhodes before he can execute Bellamy. Later, more colonists from other dropships arrive, and one of the arrivals informs Wells that his father was still in a coma, with only a few hours of oxygen left when their dropship departed.

Before Sasha's funeral, Clarke reunites with her parents at Mount Weather. She reconciles with Wells but will not resume their past relationship because she is romantically involved with Bellamy.

The 100: Rebellion

A fourth novel, Rebellion, was released on December 6, 2016.[4] A month after the previous novel, Bellamy begins showing signs of what Clarke thinks is paranoia when he obsesses over small details in the woods. However, a group of self-proclaimed "Protectors" infiltrates their camp and abducts several of its inhabitants, including Wells, Glass and Octavia. As Clarke and Bellamy organize a rescue team to take their new enemy down, their relationship is put to the ultimate test when Bellamy doesn't think Clarke trusts him.

Eventually, the rescue team and prisoners are able to take the Protectors down as a team effort and in the aftermath, Clarke and Bellamy make up and with her parents' blessing, he asks her to marry him.