Even if a body can be hermetically sealed off, clues to its location may still be obvious. American police in Indiana searching for a missing person some years ago noticed a cloud of frustrated flies hovering above a covered well. The missing person had been murdered, and the killer had thrown their remains down the well. He had sealed the well up enough to prevent insects getting in, but not the slight odour of decomposition getting out. The flies acted like a swaying gravestone, drawn to a smell beneath that was far beyond the capabilities of the human nose.
