"Knock Knock Who's There?" is the 959th episode of Casualty and the 44th episode of the 29th series. It was preceded by "The Long Haul" and followed by "Forsaking All Others - Part One". The episode was directed by Julie Edwards and written by Ben Ayrton and Matthew Barry. Tess Bateman has her final shift in the ED during the episode and makes her departure. However, her official departure is in the following episode, when she appears in a video call, still receiving main cast credit.