Sofiya Vlacic was a resident of Odessa, Ukraine, and the sister of Petro and Roman. Sofiya entered a romantic relationship with Jack Bauer when he lived in Odessa as "Borys" while hiding from the U.S. and Russian governments. That evening, Jack called Sofiya to tell her that he was helping Petro with a work-related problem. She said that her brother Roman had been missing since the previous night, but Jack assured her that he would turn up eventually. (Underground #1)