I don’t know how long it will take Octavia to return. BUT…
Bellamy and Clarke will be standing in the middle of camp, deep in discussion. The radio will crackle, and Clarke will hear someone say that a horse just came out of the woods. She’ll nonchalantly ask them to radio again when it reaches Arkadia. Bellamy will be suspicious, thinking it’s a rogue Grounder. They’ll argue how to proceed if it is. During a particularly heated moment, that radio will crackle again with a bewildered voice.
“Clarke? The horse is Helios…”
Bellamy’s eyes will go wide, and he’ll start running. He’ll run through the camp. He’ll run through the gate. He’ll run through the grasses that have yellowed from radiation. The horse will stop. The rider will awaken. And the people in Arkadia, squinting into the sun, will see a brother carrying his sister home.