While in the Merryvine Estate house, there is a flickering on the ground that flashes a brief light blue. This is a near constant occurrance and seems related to the camera angle. I managed to catch a screenshot of this mid-flicker.

Note: Where I am stood the stairs are actually buried, starting from where the shadow is on the stairs.
PC EU
Never get involved in a land war in Asia - it's one of the classic blunders!