Leonardo Vetra was a scientist that was working at CERN (European Organization for Nuclear Research) in Geneva, Switzerland. Before joining CERN, Leonardo was a priest and often attended Vittoria's orphanage. Leonardo was obsessed with Galileo Galilei's work and decided to join CERN in order to merge both religion and science together. When Leonardo got a request to work at CERN, he adopted Vittoria and both of them moved to Geneva, Switzerland.
Both Leonardo and Vittoria became physicists and were often involved in each other's work. Vittoria and Leonardo created the substance antimatter from nothing and Leonardo achieved what he set out to do by proving that something can be created from nothing. Leonardo took this new invention and method seriously and upgraded security into the lab by adding retina scanners for Vittoria and himself. Leonardo and Vittoria secretly mass-produced a large amount of antimatter and kept every CERN employee in the dark. When Leonardo was murdered by the Hassassin, he cut out Leonardo's eye and used it to steal the antimatter.
His character is replaced in the film adaptation with that of Silvano Bentivoglio, an elder and supposedly fatherly colleague to Vittoria, portrayed by Carmen Argenziano. He is seen wearing a reverend's collar during the process in which the antimatter is extracted, implying he is deeply religious, and is subsequently killed by shooting and having his eye cut out to access the antimatter.