jalima I am full of admiration for anyone that can come up with any sort of theory as to what is going on at the moment
My theory is probably completely way off beam 
I started getting confused when they introduced 2015.
Sometimes the only way I could keep up with the year was by the length of Keeley Hawes's hair!
I don't think the army officer Eve? was pregnant by Sam the first time, their affair started after Alice/Sophie/Lena had died in the shed. The first was the surrogate baby she handed over to her sister and bil. This one is Sam's baby (we presume).
In the bedroom where Alice/Sophie and little Lucy were locked in then drill man said she would be going away and she wanted Lucy to go with her, but he said no, Lucy would be staying with him.
So the girl in Switzerland is Alice/Sophie
He presumably kept Lucy to blackmail Alice/Sophie into not going to the police and revealing all. She has to phone in every day.
Surely the 3rd girl was Lena, not a boy?, and Alice/Sophie in Switzerland threw her spectacles on to the fire - symbolic of the fire that Lena died in because it was her in the shed? Drill man would have come along and let her out of the shed and replaced her with a dead body.
I think.