Talk:Mount Weather/@comment-24670104-20150823163015/@comment-26247132-20150823213235

My guess is Common Sens. The Grounder Scouts probably kept an eye on the Mountain after Lexa retreated and saw all the Sky People leave it alive. There's also the lack of seeing any Mountain Men in sight over the next 3 months after they were supposed to be "cured" by the Sky People.

Or maybe Octavia and/or Lincoln tell Nyko or Indra. Or Emerson runs into some Grounders and tells them about it.