The Steward was the man who helped Rosanna Calvierri and Francesco during the time of the 'apparent' re-appearance of the plague in Venice in 1580. His name was identified as Carlo by Rosanna when Rory Williams and Amy Pond tried to infiltrate the Calvierri manor to find out what was happening to the local girls to help give reassurance Guido that his daughter, Isabella was safe. Later on, after the failed attempt to out the Vampire girls, Carlo witnessed the death of Isabella at the hands of the Saturnynian males who were in the water.
Despite having taken part in his masters' machinations and rituals, Carlo did not seem to have known their true nature. He seemed bewildered by Rosanna's appearance when her perception filter began to fail. As her plans for Venice became clear and a storm appeared over the city, he escaped the manor with some valuables. His ultimate fate following Francesco and Rosanna's deaths remains unknown. (DW: The Vampires of Venice)