Was the story really so simple? *spoilers*
I noticed from the beginning the story seemed to take many twists and turns and when the final ending came on episode 3, it didn't make much sense to me.
The overlords were supposed to help humanity achieve peace/harmony and then facilitate mankinds evolution, by having the evolved children join the overmind.
But, it also had heavy religious overtones and from my memory of the bible, which is limited, it also seemed to suggest they were false prophets (Think that's the term) sent by the devil to confuse/deceive us.
It almost seemed to me like the overmind was an alien form of Satan , sending this alien race to wipe out humanity in some fashion and because we turned away from god, by embracing the gifts/improvements in our lives, god let it happen..
A few things stood out in the story, in the first episode Karellen said he came to earth, because we were on the verge of discovering interstellar travel and that the stars were not for man.
The alpha/prime child who had the power to control/influence other children, seemed to be created by that probe which was scanning the female while she slept.
She herself said she wasn't pregnant, implying the couple never had sex, so the aliens impregnated her, which is a lot like other devil/devils child being reborn movies in the past.
Then there's the Ouija board and that womans cross being crushed/mangled, the violence against the dad from that kid and the doctor who also got thrown against a wall.
The whole story just seemed, to me at least, to be about the devil basically killing us all off, by using the aliens advanced tech to effectively enslave us into believing they were our saviors.
Probably looking into it too far, mind you :P