Question

Read the following passage carefully:

*The afternoon heat had settled in the dust of the parlor, thick and smelling of dry lavender and old newsprint. Clara did not look at the letter on the mantelpiece; she had no need to, for its words had already burned their shape into the back of her eyelids. Instead, she watched the slow, mechanical transit of a beetle across the windowsill, its dark shell catching the amber glare of the sinking sun. It was the same window through which, six years ago, she had watched her brother’s carriage disappear down the gravel drive, the dust rising in pale plumes like smoke from a dying fire. He had promised to write weekly, yet only three such envelopes had ever crossed the threshold, their ink fading as quickly as his resolve. And now, this fourth—bearing a postmark from a port town he had sworn never to visit—lay quiet under the brass clock. The clock struck five, its chime flat and metallic, shattering the silence of the room and prompting Clara to finally reach out. As her fingers brushed the rough paper, she recalled the frantic packing of his leather valise in the dead of night, the whispered warnings she had barely understood, and the sudden realization that this letter did not mark a return, but rather the closing of a door she had spent years trying to keep open.*

In the passage, how do the narrator’s shifts between Clara’s immediate surroundings and her memories of her brother’s departure function structurally?