Fiona Payne is the former girlfriend of Derek Grant and a fellow witch hunter.
Fiona arrived in San Francisco to check on Derek on behalf of his father. Once she observed Derek with Phoebe Halliwell, she became concerned that he might be developed actual feelings for her. Her unexpected arrival also caused to Phoebe starting to distrust Derek, leading to Eros manipulating them both and exposing Derek's secret. After Phoebe left, Fiona arrived at his apartment and questioned his commitment to the cause.
Fiona took over the Mather Corporation, which angered Dr. Nichols. When Fiona and Derek discovered that Nichols had another facility and planned to execute the witches there, Brandt tried to kill them on Nichols' orders. They fled to Derek's apartment, where they ran into Piper, Phoebe and Darryl Morris, who were looking for clues to find Paige after she was kidnapped.
Fiona managed to hack Nichols' files to find his facility, though hunters attacked the apartment building. Darryl and Fiona got seperated from the others and he took her to the station. Piper and Selena later went to Fiona for the location and left her behind. Fiona then knocked out Darryl and called Derek. Along with Phoebe, they then confronted Nichols and Derek was forced to shoot him. Fiona found some blood samples Nichols took from Paige and took them for her own research.
When a teenager named Ian Griffin used magic to defend himself against bullies, Fiona ordered her hunters to capture him so he could be a test subject. However, she agreed to let him go after Derek asked her as a favor to Phoebe. Derek later visited Fiona and agreed to help her eliminate magic, so it would not stand between him and Phoebe.