"To Love You So" is the 589th episode of Casualty and the 48th and final episode of the 21st series. It was preceded by "Seize the Day" and followed by "My First Day". The episode was directed by Robert Knights and written by Gaby Chiappe. It sees the final appearance and death of Selena Donovan, portrayed by Elizabeth Carling. Additionally, Peter O'Brien makes his final appearance as Theo "Stitch" Lambert.