“Hakeldama” is episode five of season three of The 100.
In the previous episode, “Watch the Thrones”, the Ice Queen was surprisingly killed after Lexa defeated, but didn’t kill, Roan in the fight. Instead, she killed the Ice Queen, making Roan the new king.
Lexa and Clarke are heading to Camp Arkadia with the Ice Queen’s body to seal the peace. Unfortunately, that’s not going to happen. Pike, in a surprise turn of events, was elected Chancellor, and one of his first actions was to take a number of people with automatic weapons to go out and attack the army that Lexa had sent for their protection.
Pike slaughtered all 300 of the Grounders, including wounded, sparing only Indra, at Bellamy’s insistence, in order to send a message to the other Grounders. Bellamy himself is rather troubled by what they did; Pike is not. Kane sends Octavia out to meet with Indra and the Grounders, as Clarke tries to stop a war happening, as Lexa is summoning all the members of the Coalition to attack Camp Arkadia. Pike seems to think that he will be able to kill them all; this seems overly optimistic and a bit bloodthirsty. Octavia smuggles Clarke into the camp, where she tries to convince Bellamy to stop things. Bellamy is really hurting from constant loss, though.
Jaha has finally arrived back at Arkadia, but his sole Grounder companion is killed at the gates. His belief in the City of Light seems almost religious in its fervour. He is still accompanied by the AI, Alie, but no-one else can see her. Pike is a bit threatened by him, but allows him to basically proselytise. Jaha is promising a world free from pain in the City of Light, and starts off by targeting Raven, who is in constant pain from her injured leg. All you have to do, according to Jaha, is to take a pill (memories of the Matrix there).
Murphy and Emori are robbing travellers, which presents its own hazards.