Born into a two-parent family, Casey had a regular upbringing in North London. She had an older sister, Anna, but she disappeared to a yet to be revealed time and place, DW: Return of the Sister. She attended Coal Hill School which she left to study at college. She then dropped out of college to get a job as a fashion model, which did not work out.
With no job or qualifications, Casey moved back to her mum, with her dad having left her mother a year in advance not long after Anna disappeared. Casey then started a career in a local hair salon, but the pay was not that good and she longed to travel.
She travels to the 1980s and discovers a mysterious alien song which steals the lives of anyone who hears it, DW: Death by Music, visits her own grave in 2031, DW: This is Your Life, goes in search of the Highgate Vampire, DW: The Haunting of Highgate and encounters the Celestial Toymaker and his House of Horror where she and the Doctor become trapped with various old foes, DW: House of Horror.