97 years have passed since the nuclear war and the destruction of Earth, 100 juvenile delinquents are sent back in order to see if the planet is habitable.
Jasper could still be alive, the rest of the gang decide to start looking for him. Abby is determined that the planet is habitable, she does everything in her power to convince the rest.
Wells, Finn, and Clarke go out to look for a plant for Jasper’s wound as a dangerous fog approaches. Bellamy at the same time takes a group for hunting.
Charlotte kills Wells, everyone finds out. Bellamy, Finn, and Clarke protect her. In the meantime, on the Ark Abby risks drowning so she could give Raven the chance to launch the escape pod. Raven crash lands on Earth, now the plan to contact the Ark has started. Abby exposes Kane’s plan to reduce the population on the Ark.
Raven and Clarke ask Abby to help them find Finn, at the same time Bellamy tortures Grounder. Jaha surprises the council with a big revelation.
Shumway secretly orders one of the 100 to kill Bellamy. Bellamy and Clarke find military weapons. In order to bring peace, Finn arranges a meeting with the leader of the Grounders. A sceptical Clarke warns Bellamy, Jasper and Raven follow the to the meeting but with weapons.Murphy returns to the camp with a terrible virus created by the Grounders, they plan to attack the next day. Raven deals with splitting up with Finn, Clarke and Finn come face to face with a new enemy. Jaha makes a plan to come to Earth.
The remainder of the 100 face off with the Grounders, Jaha makes a noble sacrifice, that helps the Ark coming to Earth.
