MOO, pure speculation, perhaps something happened with the child which caused Aaron to panic. Maybe this was related to her medical condition or maybe there was an accident of some kind during this alleged fishing trip. Somehow he mentioned this to Nadia (voice call? Text? DM on social media? As far as I can tell, we haven't yet heard if her phone was wiped of data...), advised her he would likely be going "on the run," and they subsequently made a hasty decision to abscond together. IMHO, 21 and 22 are still very young ages and scary situations can make for drastic, even thoughtless, decisions on the fly - regardless if the subjects are generally intelligent, well-rounded people or not. I wholeheartedly hope that whatever decisions were made, and wherever they have gone, they will come to their senses and "turn themselves in," for lack of a better term - healthy and unharmed.