They arrive to the new planet with two suns. They found an empty settlement on it. Shaw died randomly in the first ten minutes (he and Raven had sex in the first five minutes of e1). There was a children's book about toxin that's activated by the eclipse of the two suns. After that they started to experience the effects, went crazy and tried to kill people closes to them (Emori tried to kill Murphy, Bellamy tried to get to Clarke, Echo and Murphy, Clarke tried to kill herself).
There was also a flashback to 238 years prior to that, to the first colony, where a head scientist killed his wife and the entire colony, and attempted to kill his daughter (she named the planet Sanctum) due to the eclipse psychosis. These three people are highly regarded by the present day colonists, for some reason.
In the present day the space ship was overrun by four people from the planet but Raven asked Dyioza (and Madi, because reasons??) to help to get rid of them. The lady who left led the Eligius crew to the settlement where Clarke and co were.
Octavia tried to commit suicide via crowd beating. Meh.
Kane is in stasis again because he's in a bad way.
Raven hates Abby. Murphy and Emori hate Clarke. Bellamy dislikes Octavia.