What is the importance of the burn marks in Hundreds Hall in the novel, The Little Stranger?

The burn marks are a symbol of the poltergeist that Caroline and Roderick believe is haunting Hundreds Hall. The marks appear on the back of the door into which Roderick walked and blackened his eye; the footstool, over which Roderick tripped and sprained his wrist; and above the washstand where Roderick’s lost collar and cufflinks fell mysteriously into his washbowl.