Geraldine Somerville as DS Jane Penhaligon (Series 1-3): Fitz's main love interest throughout the series, after she unwillingly falls for him in "To Say I Love You".
Tess Thomson as Katy Fitzgerald (Series 1-3, special episode "Nine Eleven"): Fitz's daughter, who goes to live with her mother and grandfather each time Judith walks out on Fitz.