"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.
After what happened with Louis last week Charlie feels bad about Tess's Necklace and buys her a new one. Tess's son Sam soon turns up with his baby after Tess rang him last week. He soon tells her that he is looking after baby Charlie by himself and that he needs her help so she gives him the keys to her house but he wants her to move to Leeds. She doesn't want to leave but confines in Charlie and tells him she has to do it for Sam.
After Dylan calls Lofty incompetent Rita tells Zoe that she has to confess to Connie about how Dylan has been behaving. Robyn tells Lofty that he should make a complaint but Lofty doesn’t want to hear it. Connie tries to talk to Dylan offering him some time of for a while but Dylan isn't having any of it and now has to prove himself to Connie but can he do it?.
When Richard spots a boy breaking into his factory he chases after him but after climbing many platforms they both Fall the boy manages to escape but Richard has to call for an ambulance Ian and Dixie take him back to the ED. The boy that tried to break in ends up in the ED with a deep wound on his arm. Lofty removes something from the wound but when the boy (Josh) finds out that Lofty and Jacob are nurses he gets cocky knocking all the equipment on the floor. Lofty cleans his wound but when Lofty tries to get his own back Josh has a panic attack and ends up hitting lofty in the nose. Richard wants to see Josh and makes him do his job while he is in the ED. But when he tries to rush off Jacob manages to stop him and gets the truth out of him, Richard wants him to go and open a container. Jacob is happy and goes to confront Richard but the stress causes him to into VF, Dylan uses an LMA when shocking and CPR fail, After more shocking and CPR they manage to revive Richard. Richard pulls the metal from his leg in order to go after his wife but he ends up bleeding heavily instead when he hits an artery but Dylan isn't coping and heads to the floor for his notes, Connie sees him and she isn't happy.
Dixie and Ian take Josh back to the factory to help get the people out of the container but when they need a key it seems like Josh has done a runner, but in fact he went to the office to get the key. They find 3 people. The First a woman dies after she goes into VF and Dylan doesn’t take it to well.
Derek is brought into the ED after he chokes on a sweet when out for chips with friend Rose. He is complaining of chest pains and when Ethan takes a look Derek has serirosis all over his body, when Rose walks in he is mortified but she later tells him that it doesn't matter to her
After Robyn tells Rose that she should fight for Derek, Ethan realises that he needs to fight for Honey and just ask her out. He asks a Stunned Noel's permission and when Honey over hears she is delighted and they Kiss.