At the begining of the show, when he was telling her to draw the picture, I had an image of a circle in the middle. First a flower, then a more abstract design. So there was clearly something in what he was saying to suggest the circles.
When he gathered the poeple in the museum, before they drew, he kept mentioning "sight", "looking", "viewing", the "isolation tank" (several times), and the museum staff keeping an "eye* on proceedings.
Then the camera zoomed in on her eyes (which had a very distinctly dark edge to the iris - to the extent that I though she might be wearing cosmetic contacts).
I didn't pick up the Stonehenge thing, but it must have been in there somewhere.
He never explains anything though, does he? Git.