Double, Double, Toil and Trouble - S4.E4

Endora is fed up. Samantha's loyalty to her marriage is keeping her from her responsibilities as Queen of the Witches. While Samantha is out, Endora calls Serena to impersonate Sam and make a shambles of their marriage. Darrin finally realizes that it is Serena, and plans on turning the tables--only the real Samantha has arrived home.