She thought a while and answered:  ’It may be done, for as it chances the wording of my absolution will cover it.  But you must come cowled as a priest, that those who carry out the sentence may know nothing.  Still others will know and I warn you that should you speak of the matter you yourself will meet with misfortune.  The Church avenges itself on those who betray its secrets, senor.’

‘As one day its secrets will avenge themselves upon the Church,’ I answered bitterly.  ’And now let me seek a fitting drug—­one that is swift, yet not too swift, lest your hounds should see themselves baffled of the prey before all their devilry is done.  Here is something that will do the work,’ and I held up a phial that I drew from a case of such medicines.  ’Come, veil yourself, mother, and let us be gone upon this “errand of mercy."’

She obeyed, and presently we left the house and walked away swiftly through the crowded streets till we came to the ancient part of the city along the river’s edge.  Here the woman led me to a wharf where a boat was in waiting for her.  We entered it, and were rowed for a mile or more up the stream till the boat halted at a landing-place beneath a high wall.  Leaving it, we came to a door in the wall on which my companion knocked thrice.  Presently a shutter in the woodwork was drawn, and a white face peeped through the grating and spoke.  My companion answered in a low voice, and after some delay the door was opened, and I found myself in a large walled garden planted with orange trees.  Then the abbess spoke to me.

‘I have led you to our house,’ she said.  ’If you know where you are, and what its name may be, for your own sake I pray you forget it when you leave these doors.’

I made no answer, but looked round the dim and dewy garden.

Here it was doubtless that de Garcia had met that unfortunate who must die this night.  A walk of a hundred paces brought us to another door in the wall of a long low building of Moorish style.  Here the knocking and the questioning were repeated at more length.  Then the door was opened, and I found myself in a passage, ill lighted, long and narrow, in the depths of which I could see the figures of nuns flitting to and fro like bats in a tomb.  The abbess walked down the passage till she came to a door on the right which she opened.  It led into a cell, and here she left me in the dark.  For ten minutes or more I stayed there, a prey to thoughts that I had rather forget.  At length the door opened again, and she came in, followed by a tall priest whose face I could not see, for he was dressed in the white robe and hood of the Dominicans that left nothing visible except his eyes.

‘Greeting, my son,’ he said, when he had scanned me for a while.  ’The abbess mother has told me of your errand.  You are full young for such a task.’

’Were I old I should not love it better, father.  You know the case.  I am asked to provide a deadly drug for a certain merciful purpose.  I have provided that drug, but I must be there to see that it is put to proper use.’