Optatus Gracilis was a young man of 16 who was the son of Gnaeus Gracilis and Marcia Gracilis. Being the son of a wealthy man, he was in the process of getting an education and was well taken-care of. At one point, he had fallen from a peach tree and broken his arm, which never set right, leaving him with a disfigured lump on his lower arm. In 120, his father wanted to build a statue to celebrate his coming of age, and commissioned Aulus Valerius Ursus to sculpt it. However, on the day the Ursus said the statue only needed a few final touch-ups, Optatus went missing. The statue was still placed in the centre of a garden in their home anyways.
When Optatus disappeared, his father went all around Rome and its outskirts trying to find him. Eventually, he found a fortune teller who could see the future after meeting the Tenth Doctor and Rose. Believing the fortune teller could find his son, she was brought to the villa, and from that point she, the Doctor, and Rose began their investigation to find him.
Eventually, the Doctor realised that Ursus had the ability to turn people to stone, more specifically, marble, and had done so to Optatus for a large lump sum of money. During the confrontation with the GENIE, the GENIE filled an empty vial of what was green liquid that had already been used up and had the ability to reverse the petrification process, despite no liquid ever having been formulated. When the liquid was used in Optatus' statue, he reverted back to flesh and bone, and his family was overjoyed. Only Gracilis knew what had actually happened, deciding to keep the information from his wife in case it disturbed her mind. (PROSE: The Stone Rose)