One of the cells of Palazzo Chiaramonte Steri's prisons in Palermo still bears the marks of drawings depicting saints and martyrs accompanied by hand-written prayers and hymns in Latin. Interestingly, each single drawing is marked with a letter B. According to Giuseppe Pitrè, these graffiti should be attributed to Francesco Baronio Manfredi, an erudite priest who was arrested by the Spanish Inquisition in 1647 after the revolt of Palermo. What are the reasons behind his arrest? Why is he considered to be the author of graffiti depicting saints and martyrs? Starting from Pitrè's hypothesis, I will investigate Baronio's past in order to understand the reasons for his imprisonment. At the same time, I intend to shed new light on the graffiti that he supposedly drew during his imprisonment.