What happens to the story of the Cavalier's death?

The opening of the sixteenth chapter reveals a little more of the truth behind the story of the Cavalier's end as Biagio recounts the much simpler story Cosimo tells when he first returns to the trees with Ottimo Massimo carrying the truncated head. In that story, the Cavalier is merely kidnapped by the pirates, but that story saddens his father so observably that he later invents a story of cunning on the part of the Cavalier in order to entrap the pirates, but it is too full of holes to be sustained.