My old mentor, Antonio Calvi, had taught me well that no tool in medicine is more powerful than observation. God created man, Antonio would say, but He left it up to us to heal each other, without revealing the secrets of His creation. We do most of our mending in the dark, stumbling for our way like the blind. If one happens across a treatment that helps one patient, it will likely help others.

Unlike Don Marco, I refused to believe that God would choose to spare rats from this pestilence above all other creatures. There had to be an earthly secret to their salvation. Something that must dwell within the humors of the rodent. Perhaps that protection could be shared, I reasoned. I felt compelled to find out.

I waited several hours while I forced more water and even a little wine into my objecting stomach, as I hoped to rally a modicum of strength. But it was to no avail. I realized that I would only grow weaker. There would be no better time to visit San Giovanni.

The journey on foot up the hill to the monastery was the most taxing of my life. Every ten paces or less, my legs and lungs demanded rest. At some point, I collapsed on the path just as a farmer’s family approached from the opposite direction. The father steered his cart off the path to avoid me while the mother wrapped her children’s faces in cloaks as they passed. Eventually I summoned the energy to rise and finish the trip. I collapsed again in the wet dirt outside the gates of the monastery. Don Marco himself found me there.

Even though he must have seen in a glance that I was afflicted, Don Marco sat down at my side and revived me with sips of warm cider from his wineskin. Unconcerned about my contagiousness, he lifted me to my feet and supported me with his body. Leaning heavily on him, I shuffled inside the monastery and slumped into the first chair I reached.

Though it was still daytime, the room was warmed by a roaring fire. And for the first time, I witnessed black-cloaked brothers performing functions other than tending the sick or dying themselves.

Don Marco appeared as hale as ever. His mood was, if possible, even more ebullient than before.

Our humble home has been blessed! he said. We have not lost a brother in almost two days. And no one else has fallen ill in almost twice that time. It appears that the accursed infliction has tired of our monastery and moved elsewhere.

That is remarkable, I said.

And you, good doctor! Your visits have been almost as restorative as our Savior’s intervention. But clearly you are afflicted now, too.

Yes, as of this morning.

Then the least we can do is tend to you as you have for us.

No, Don Marco, I am not staying.

Then why have you journeyed this far, as ill as you are?