I don't know if anyone else has thrown this theory out there yet.

It came to me that the hatch on top of the "whatever it is" which we saw again tonight is pretty small. Then I started thinking about that Disney movie The Rescuers. The plot of this "mouse driven" film isn't really important, but it revolves around an orphan named Penny who is kidnapped by an evil woman and forced to go down into a tiny cave day after day to look for a hidden diamond. Penny was the only one who could look because the adults were too big. They needed a small person.

What if Ethan and the others have a hatch too. They have it open, but they are all too large to get into it. They could see Claire's baby as an opportunity. Take the child, raise and train the child to look for what ever it is inside the hatch.

Just a thought. Flame away. :)