Fans of the soap recently saw Derek's daughter Alice get cold feet over building bridges with him, having been warned off by Tanya during a private conversation in the Brannings' kitchen.
Next week's episodes see Derek (Jamie Foreman) start to realise that somebody must have scared Alice off at the recent party. When he notices that a guilty Tanya is ignoring him, Derek puts two and two together and figures out that she was responsible.
Backed into a corner, Tanya (Jo Joyner) is forced to admit that she told Alice the truth about Derek, which infuriates the Walford bad boy.
Fortunately for Derek, Alice agrees to see him again following some encouragement from Lauren and Cora. Derek then tries his best to win Alice round by explaining that Tanya is simply "deluded".
Confronting Tanya later, Derek declares that he won't let her get away with spreading poison and if she goes any further by sticking the knife in, she's dead… How will Tanya react?
EastEnders airs these scenes on Monday, May 28 and Tuesday, May 29 on BBC One.