Pulbius or Vulcan is the son of Rectina and a friend to the four detectives.
Vulcan is a handsome sixteen-year-old blacksmith and Christian who travels through Pompeii with his donkey. His name is in fact Pulbius, but due to his trade and his deformed foot he is nicknamed Vulcan after the lame god, which he detests but puts up with anyway. He, like so many others, becomes entranced by Miriam's beauty and makes her a silver bracelet as a token of his affections. He turns out to be the long-lost son of Rectina and her husband, the latter who left him to die on the banks of a nearby river when he believed that Rectina had been having an affair with Pliny. However, a slave girl found him and took him to her master, who allowed one of his freed slaves to raise him as his own.
Vulcan is a solemn, subdued boy who rarely smiles but is very kind-hearted and understands morals a lot better than Flavia or her friends do. When he asks Flavia what her ideal treasure is, she replies material goods, which disgusted him.
Vulcan is handsome and muscular. He has very dark, thick eyebrows that almost meet in the middle.