Final answer:
The flashback provides an impressionistic and filmic quality to the passage, offering insight into Isabella's character and complementing the narrative's themes.
Step-by-step explanation:
The flashback describing Isabella's first assignment adds depth to the narrative by providing background information and insight into her character and experiences. This technique creates an impressionistic feel, suggesting a scene akin to a filmic sequence with its detailed yet somewhat vague and fluid description. The transitional nature of the narrative, like the shift from a man's internal thoughts to direct speech, mirrors the character's journey and underscores thematic elements of memory and perception within the passage as a whole.