Imprimatur

Embarrassed, I confessed to him that I also used good oil, because we had it in abundance, while the impure oil mixed with dregs was in short supply.

Abbot Melani could not hide a sly grin. 'Now don't lie: how many lanterns have you?'

'To begin with, we had three, but we broke one when we were climbing down into the gallery. There are two left, but one needs a little mending.'

'Good, take the better one and follow me. And take that too.'

He pointed at a rod, leaning vertically in a corner of the chamber, with which in his rare free moments Signor Pellegrino was wont to go fishing on the banks of the Tiber, just behind the little church of Santa Maria in Posterula.

A few instants later, we were already in the closet, and had entered the well that gave access to the stairs leading down to the underground galleries. We lowered ourselves with the help of the iron rungs set into the wall until we felt the brick platform under our feet, and then we took the square stairwell. At the point where the stairway was excavated directly from the tufa, we encountered again the coating of slime on the steps, while the air became heavy.

At last, we reached the gallery, deep and dark as the night in which I had discovered it.

As I followed him, Abbot Melani must have felt my curiosity as though I were breathing down his neck.

'Now at last you will know what that strange Abbot Melani has in his head.'

He stopped.

'Give me the rod.'

He laid half the cane across his knee and with a sharp movement snapped it in two. I was about to protest, but Atto stopped me.

'Do not worry. If you ever have to report this to your master, he will understand that this was a matter of emergency. Now, do as I tell you.'

He made me walk in front of him, holding the broken cane vertically behind me and dragging the end of it along the vault of the gallery, like a pen sliding on paper. Thus we advanced for a few dozen cane's lengths. Meanwhile the abbot asked me some bizarre questions.

'Does oil mixed with wine dregs have a special taste?'

'I would not know how to describe it,' I replied, although in reality I knew the taste perfectly well, having more than once furtively sprinkled some onto a slice of bread purloined from the pantry, when Signor Pellegrino was sleeping and the meal had been too frugal.

'Would you call it rancid, bitter and acid?'

'Perhaps… Yes, I'd say so,' I admitted.

'Good,' replied the abbot.

We advanced a few paces further, and suddenly the abbot ordered me to stop.

'We are there!'

I looked at him in some perplexity.

'Have you still not understood?' he said to me, his grin queerly deformed by the lamplight. 'Then let us see if this will help you.'

He took the cane from my hands and pressed it hard against the vault of the gallery. I heard something like the groaning of hinges, then a tremendous reverberation, and finally, the skittering of a little shower of dirt and stones.

Then terror struck: a huge black serpent lunged at me and almost seized me, after which it remained grotesquely suspended from the ceiling like a hanged man.

I withdrew instinctively with a shiver, while the abbot burst out laughing.

'Come here and bring the lantern closer,' he said triumphantly.

In the vault, a hole appeared, almost as wide as the entire cavity; and from it hung a thick rope. This was what, tumbling down when the trap opened, had brushed against me and terrified me.

'You let yourself be frightened by nothing, and for that you deserve a little punishment. You will go up first. Then you will have to help me up after you.'

Fortunately I succeeded in climbing up without too much difficulty. Clinging to the rope, I swarmed up it until I reached the upper cavity. 1 helped Abbot Melani to join me there and he marshalled all his strength, twice coming close to dropping our one and only lantern.

We found ourselves in the middle of another gallery, aligned obliquely to the first one.

'Now, it is up to you to decide: right or left?'

I protested (weakly, fearful as I was): was this not perhaps the moment for Abbot Melani to explain to me how he had worked all this out?

'You are right, but then I shall choose: let us proceed to the left.'

As I myself had explained to the abbot, oil mixed with dregs generally has a far less agreeable taste than that which is used for frying or for good cooking. The drop which he had found on my forehead the day after the first exploration of the gallery (and which, miraculously, had not come into contact with the blankets when I lay down) could not, according to its taste, come from the lanterns of the inn, which I myself had filled with good oil. Nor did it come from Cristofano's medicinal ointments, which were all different in colour. Therefore, it came from an unknown lantern which-who knows how-must have been situated above my head. From this, the abbot had concluded with his usual alacrity that there must be an opening in the vault of the gallery: an opening which also provided the thief's only possible way out, when he had so inexplicably vanished into nothingness.

'The oil that fell on your forehead must have dripped from the thief's lantern through a crack next to the hinges of the trapdoor.'

'And the cane?' I asked.

'I was sure that the trapdoor, if it existed, must be very well hidden. But a cane like that of your master's fishing rod is very sensitive to vibrations, and we were sure to feel a shock when it moved from the stone of the gallery to the wood of the trapdoor. Which is what indeed happened.'

I was secretly grateful to the abbot for having in some way attributed to both of us the credit for having discovered the trapdoor.

'The mechanism is somewhat rudimentary,' he continued, 'but it works. The rope, which so affrighted you when it came down from the ceiling, is simply stowed on the top of the trapdoor and closed together with it. When the trap is opened from the gallery below, pushing upwards, the rope falls down. It is important to put it back in the same way when one returns if one wants it to be available again.'

'Then you think that the thief always moves back and forth along this gallery.'

'I do not know; I suppose so. And I suppose too, if you wish to know, that this gallery leads somewhere else.'

'Did you also suppose that solely with the aid of the cane we should find the trapdoor?'

'Nature makes merit, but fortune sets it to work,' pronounced the abbot.

And by the faint light of the lantern the exploration began.

In that gallery, too, as in the one we had left beneath us, a person of normal stature was obliged to stoop slightly because the vault was so low. And, as we at once observed, the material of which it was built, a pattern of diamond-shaped bricks, seemed identical to that of the previous gallery. The first stretch went in a long straight line which seemed gradually to slope downhill. 'If our thief has followed this track, he must be strong and fit,' observed Abbot Melani. 'Not everyone could climb that rope and the terrain is rather slippery.'

Suddenly we both suffered the most atrocious fright.

A stranger's footfalls, light but utterly clear, were approaching from a point which could not be identified. Atto stopped me, squeezing my shoulder hard, to signal the need for extreme caution. It was then that a reverberation caused us to tremble, similar to that when we had opened the trapdoor through which we passed not long before.

Hardly had we recovered our breath than we looked at one another, our eyes still wide with anxiety.

'Do you think it came from above or below?' muttered Abbot Melani.

'More above than below.'

'I'd say so, too. So it cannot be the same trapdoor-it must be another one.'

'And how many do you think there are?'

'Who knows? We were mistaken not to explore this ceiling too with the cane. Perhaps we might have found