Levitt is back in MCAP dealing with the guard who was there during Bellamy's "death". He is suffering from PTSD so Levitt goes into his mind and spots that Bellamy wasn't killed, he was blown into the Anomaly. 

Anders turned the Anomaly Stone to Etherea, which is where Bellamy ends up with the Conductor he held hostage. 

The Conductor attacks him, so Bellamy defends himself and that turns into the Conductor breaking his leg. Bellamy looks after him and nurses him back to health, because he knows they need to work together to get out of there.

His leg heals and they make it up the mountain but then a snow storm hits. Bellamy almost dies of frostbite so the Conductor saves him and they camp out in a cave. They find a room full of strange light forces, which the Conductor explains is the next step to transcending that Cadogan wrote about to his followers. He went through Etherea and discovered this, which is what everyone is working towards becoming.

Bellamy feels their power but he denies Cadogan and what he saw, he can't agree with preparing for more war or letting go of his feelings for his loved ones.

But then two months pass as they wait out the snow storm, and Bellamy turns to prayer with the Conductor. He sees a vision where Cadogan speaks to him and shows him Aurora, and she tells Bellamy to go towards the light. Bellamy then opens his eyes and the storm cleared, so he starts to believe.

Bellamy and the Conductor use their belief in Cadogan to get to Etherea's mountain with the stone, and they return to Bardo. Bellamy bows to Cadogan, and gets taken to Clarke and the others. 

They are being held in Cadogan's quarters because he still believes that Clarke has the key. Clarke is about to tell Cadogan she will help him as soon as he sends everyone else back to Sanctum, but he shows them Bellamy first. 

Clarke hugs Bellamy and warns him about the key being the flame. Bellamy tells Cadogan the truth about the key not existing in front of everyone, showing that his allegiance is to Cadogan now.