Question

Read the following passage carefully:

Julian did not look back. The air of the Deep District was heavy with coal dust and the sulfurous breath of the furnaces, a subterranean fog that clung to the damp stone walls of the passage. Behind him, the light step of Clara was a fragile thread keeping him anchored to his purpose. The overseer’s contract had been clear, whispered in the cold vault of the administrative office: 'Take her, but do not turn to verify her presence until the sunlight of the Upper Terrace strikes your brow. To doubt is to forfeit.'

With every step up the winding, shadow-choked stairs, the silence grew heavier. It was a silence that seemed to hum with the voices of the forgotten, the thousands who labored in the dark below. Julian’s lungs burned, yet he pressed upward, his eyes fixed on the distant, pale blue rectangle of the surface world. He could hear her breathing—or was it merely the sigh of the ventilation drafts traveling through the shafts?

A sudden chill draft swept down the stairwell, carrying with it a sound like a muffled sob. Julian's heart seized. Had she stumbled? Was she being pulled back by the silent watchers who guarded the threshold? The doubt, a small spark in the darkness, flared into a consuming panic. Just three steps from the threshold, where the first pale beams of morning light began to illuminate the dusty stones beneath his feet, Julian halted.

'Clara?' he whispered.

He turned.

In the half-light, her face was a pale cameo, her eyes wide with a sorrowful, sudden understanding. As the light from the surface caught her hand, it seemed to dissolve into the gray mist of the shaft. She did not cry out; she simply drifted backward, down into the shadows of the Deep District, leaving him alone on the threshold of the sunlit world, his outstretched hands grasping nothing but the empty, soot-choked air.

In the passage, the structural parallel to the myth of Orpheus and Eurydice primarily serves to achieve which of the following effects?