Going to the window, she saw the sky grown black with thunder clouds.

So quickly the storm gathered, that the bright summer world without seemed suddenly hung over with a deep purple pall.
Birds screamed and darted by, on hurried wing; then, reaching home, fell silent.

All nature seemed to hold its breath, awaiting the first flash, and the first roll of thunder.
Still standing at her window, the Prioress questioned whether the nuns were returned, and safely in their cells.

While underground they would know nothing of it; but they loved not passing along the cloisters in a storm.
The Prioress wondered why she had not heard the bell announcing their return, and calling to the hour of prayer and silence.

Also why Mary Antony had not brought in the key and her report.
Thinking to inquire into this, she turned from the window, just as a darting snake of fire cleft the sky.