I had something weird happen to me yesterday. I heard a battle going on and I went to see what was going on and this guy Tom opens up and fires on me so I killed him as I usually do with people who shoot at me and then the other guy started shooting at me too! So I started shooting back and he had a name too and it was Tom. I looked and they were identical. Same face, hair and clothes except one of the Toms had a Synth component. My settlers are being killed off and replaced by Synths, OMG! I don't think there is any way to tell the Synths apart from the humans.
Just today I tried to use my Pacify perk and my gun went off in a settler's face. Curie got really mad and stormed off and when I tried to catch up she tried to kill me. I used a Save point to start over again but Curie doesn't have a lot of hit points. She's easily killed if necessary. She wouldn't let me Stimpak her either. Maybe it's time to get the big robot out and destroy the Institute for good. That would definitely make Curie mad.