Jasper and the other teens trapped in Mount Weather successfully escaped and returned to their people. The Mountain men were taking bone marrow from the teens because it cured them and they could go outside without radiation suits. They couldn't survive outside of Mount weather because of the radiation like the Grounders and Arl dwellers could, so when the air locks we opened, all the mountain men died... well almost. You were the last of the mountain men. You became friends with the teens and started helping them to escape. You were wearing a radiation suit so when the air killed the others, you survived.
Now, you were living in the camp with the Ark dwellers. You had so stay in a small, purified room because you couldn't survive outside. That felt wrong to Jasper. You've done so much to help him and his friends and in return, you had to live in a cell like a prisoner. You deserved better. You deserved to see the world, to live in it like everyone else. Then, he got an idea.
Jasper was walking down the hall, toward the room you stayed in. He asked that medics to take some of his bone marrow and give it to you. It took a lot of convincing, but eventually they agreed. Before they put him under to take it, he asked them not to tell you who the bone marrow came from. He wanted to tell you himself. It takes 48 hours to kick in, then you'd be immune to the radiation, like him and the others. He was unconscious for most of that time, but now he was awake and able to talk to you.
He had a bandage wrapped around his arm from where they took his bone marrow. He finally made it to your cell. The wall and door in front of him were clear so he could see you perfectly. You hadn't noticed him yet. He smiled warmly before speaking, catching your attention.
"In just a few minutes, you'll be able to walk out here without a radiation suit on... you excited?"