Ianto Jones, portrayed by Gareth David-Lloyd, is a member of the Torchwood team in Cardiff.
The first episode that focused on Ianto was "Cyberwoman" in season 1. It is revealed that his former girlfriend, Lisa, has been turned into a Cyberman and Ianto has been hiding her in the basement. She escapes and kills two people. When she knocks Ianto out, Jack revives him with a kiss. Eventually, the rest of the team manages to kill Lisa.
Jack and Ianto eventually develop a relationship, with Ianto being one of the few people that brings out Jack's empathy. The relationship tragically ends with Ianto's death at the end of season 3.