But to the Reverend Mother, guarding her flock from sin or shame, a visitor from the Unseen World held less of horror than a possible intruder from the Seen.

A rapid glance as she sounded the bell, had shown her that the passage was empty.

Which cell now sheltered two, where there should be but one?

The Prioress walked across to a recess near the south window, touched a spring, and slid back a portion of the oak panelling.  Passing her hand into a secret hiding place in the wall, she drew forth a beautifully fashioned dagger, with carved ivory handle, crossed metal thumb-guard, blade of bevelled steel, polished and narrowing to a sharp needle point.  She tested the point, then slipped the weapon into her belt, beneath her scapulary.  As she closed the panel, and turned back into the chamber, a light of high resolve was in her eyes.  Her whole bearing betokened so fine a fearlessness, such noble fixity of purpose that, looking on her, Mary Antony felt her own fears vanishing.

“Now listen, dear Antony,” said the Prioress, holding the old woman with her look.  “I must make sure that this twenty-first White Lady of thine is but a trick played on thee by thy peas.  Should she be anywhere in the Convent I shall most certainly have speech with her.

“Meanwhile, go thou to thy kitchens, and give thy mind to the preparing of the evening meal.  But ring not the Refectory bell until I bid thee.  Nay, I myself will sound it this evening.  It may suit me to keep the nuns somewhat longer at their devotions.

“Should I sound the alarm bell, let all thy helpers run up here; but go thou to the cell of Mother Sub-Prioress and persuade her not to rise.  If needful say that it is my command that she keep her bed. . . .  Great heavens!  What a crash!  May our Lady defend us!  The lightning inclines to strike.  I shall pass to each cell and make sure that none are too greatly alarmed.”

“Now, haste thee, Antony; and not a word concerning thy fears must pass thy lips to any; no mention of a twenty-first White Lady nor”—­the Prioress crossed herself—­“of Sister Agatha, to whom may our Lord grant everlasting rest.”

Mary Antony, kneeling, kissed the hem of the Prioress’s robe.  Then, rising, she said—­with unwonted solemnity and restraint:  “The Lord defend you, Reverend Mother, from foes, seen and unseen,” and, followed by another blinding flash of lightning, she left the cell.

CHAPTER IX

THE PRIORESS SHUTS THE DOOR

The Prioress waited until the old lay-sister’s shuffling footsteps died away.

Then she passed out into the long, stone passage, leaving her own door open wide.

Into each cell the Prioress went.

In each she found a kneeling nun, absorbed in her devotions.  In no cell were there two white figures.  So simple were the fittings of these cells, that no place of concealment was possible.  One look, from the doorway, sufficed.