Alright, so here is the idea. An alien race comes to planet earth and hovers in the atmosphere for a long time. They do not make any contact nor do they even attack, they just hover there. Eventually, humans start to disappear the the populations all over the world drop dramatically. It turns out that the alien race is in fact an organic mechanical race, part living being part robot. They seem to be turning humans into their own kinds. From here the reason stems of into many offered ideas such as... 1) The species is bring humans into their species because they had genetic relations, such as our DNA is somehow an decedent to them. 2) The aliens are expanding their species because they either are unable to reproduce normally any longer or because they wish to bring more variety into their species. 3) They are slowly dieing off from a plague of some kind and they are studying human genetics in hopes of developing a cure through them. Anyway, if you have any other ideas or opinions just post them in the forum!