Annie Sawyer is an insecure ghost haunting the house she lived in with her fiancé whilst she was alive. After a long period of being alone, she is joined by George Sands (a werewolf) and John Mitchell (a vampire), who are able to see her because of their own supernatural conditions. The extent of Annie's visibility to humans varies depending on her mood and her confidence.
She always appears in the clothes she was wearing when she died, which change subtly depending on her state of mind. Annie's life as a ghost has involved her coming to terms with her own death, avoiding death's door and being trapped in purgatory, in addition to several doomed attempts at romance. After losing Mitchell, the love of her life, and friends George and Nina, Annie becomes a mother figure to Eve (George and Nina's daughter) and new werewolf and vampire housemates, Tom and Hal. Annie later crosses over to be reunited with her old friends, having made a difficult decision which averted a dark future for mankind, saving the world from the Old Ones.