Fiona Carter was one of MI6's most respected officers. She constantly enjoyed shifting identities and even the lies. This chameleon quality was deeply attractive to her husband Adam, but unlike him, she shied away from introspective questioning, knowing her best work was her skill in the field. Fiona was intensely loyal both to her family and workmates but struggled with the conflict of motherhood and espionage.
Though she loved her son Wes, she would never leave the world of the Spooks willingly. Fiona originally worked at MI6, but was seconded to MI5 following Zoe Reynolds' departure. This would allow Fiona to work alongside Adam as part of Section D. Fiona had previously been married to Farook Sukkareigh, a Syrian spy.
This past life caused her ultimate downfall, as, while she was working undercover, Farook (whom she thought was dead), now a terrorist, tracked her down and, upon finding she had re-married to Adam, kidnaps her and attempts to smuggle her back to Syria. While Fiona is able to escape, Farook, before he is killed by Adam, shoots and kills Fiona. Fiona dies in Adam's arms.