<P> In the third season, Alpha Station, now renamed Arkadia, comes under new management when Pike, a former teacher and mentor, is elected as chancellor and begins a war with the Grounders . An artificial intelligence named A.L.I.E. who was commanded to make life better for mankind, is revealed to have responded by solving the problem of human overpopulation by launching the nuclear apocalypse that devastated Earth . The AI takes over the minds of nearly everyone in Arkadia and Polis, the capital city of the Grounders . In the season three finale, Clarke manages to destroy A.L.I.E. </P> <P> In the fourth season, hundreds of nuclear reactors around the world are melting down due to decades of neglect that will result in 96% of the planet becoming uninhabitable . Clarke and the others search for ways to survive the coming wave of radiation . When it is discovered that Nightbloods, descendants of first, original Nightbloods, including Becca--the creator of A.L.I.E. and the first Grounder commander--can metabolize radiation, Clarke and the others attempt to recreate the formula, but their attempts failed . An old bunker is discovered that can protect 1,200 people for over 5 years; each of the twelve clans select 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 original Ark . </P> <P> In the fifth season, which takes place six years after the meltdown of the nuclear reactors, a prisoner transport ship arrives in the only green spot left on Earth, where Clarke and Madi, a Nightblood Grounder who also survived the wave of radiation that swept the planet after the meltdown, have been living . Meanwhile, those who survived in space and in the bunker, have returned safely on the ground . Now, a struggle for the Shallow Valley, between the prisoners and a new, united clan, known as Wonkru, begins . Later, the heroes must find a way to prevent another disaster from ever happening . In the fifth season finale, however, the valley is destroyed and the surviving human race were sent to a new planet to begin their new lives . </P> <Ul> <Li> Eliza Taylor as Clarke Griffin </Li> <Li> Paige Turco as Dr. Abigail "Abby" Griffin </Li> <Li> Thomas McDonell as Finn Collins (seasons 1--2) </Li> <Li> Eli Goree as Wells Jaha (season 1; guest season 2) </Li> <Li> Marie Avgeropoulos as Octavia Blake </Li> <Li> Bob Morley as Bellamy Blake </Li> <Li> Kelly Hu as Callie "Cece" Cartwig (season 1) </Li> <Li> Christopher Larkin as Monty Green (seasons 1--5) </Li> <Li> Devon Bostick as Jasper Jordan (seasons 1--4) </Li> <Li> Isaiah Washington as Thelonious Jaha (seasons 1--5) </Li> <Li> Henry Ian Cusick as Marcus Kane </Li> <Li> Lindsey Morgan as Raven Reyes (season 2--present; recurring season 1) </Li> <Li> Ricky Whittle as Lincoln (seasons 2--3; recurring season 1) </Li> <Li> Richard Harmon as John Murphy (season 3--present; recurring seasons 1--2) </Li> <Li> Zach McGowan as Roan (season 4; recurring season 3) </Li> <Li> Tasya Teles as Echo (season 5--present; recurring season 4; guest seasons 2--3) </Li> </Ul>

When does season 6 of the hundred start