I ran this investigation yesterday for a group of three. It was really easy to set up (using notes in German I had prepared, my Italian is not good enough to run off the page), had a great flow and striking imagery. Slight SPOILERS to follow in my play report:

They were a lazy monk destined to become the next priest, an avaricious tax collector and an envious foreign mercenary. The harbour irritated them, but the church gave them quite a shock. From then on, the game just flowed. They dined with Ranieri, were unsettled by a naked Don Lapo and spent the night in fitful sleep - or, indeed, waking. Next morning, I had Elemosina serve them some warm milk in the bright morning sun for a contrast… They found the key (they rolled a 6, so it did come off the bible page, which was very nice) and went down to the crypt, where our tax collector hit Insight 5 for the third time already… 

I left the ending open, and they gave me epilogues of their characters a year after the event,  all very changed, all living in fear of the dark. The tax collector told us how, just before his death, he had saved the bible and the key had strangely reappeared. The priest had turned industrious, the mercenary had given up his envy and turned into a Savonarola-like preacher. Great stories all.