The mark on the cuff
An original fiction passage set in the nineteenth century.
Mr Drayton arrived shortly before supper and gave Marian his coat. Rain shone on its shoulders, but beneath one cuff she noticed a patch of dry white dust, like plaster. He said that he had come directly from the station, then followed his host into the dining room. Marian hung the coat in the upper passage and returned to her duties. She poured the wine steadily and replaced each dish at the proper moment. Yet, as she moved between table and sideboard, the pale mark travelled beside her, though the coat itself was two floors above.
Marian resumes her duties, but the mark continues to intrude on her attention. Identify the phrase that conveys this.