Samantha sees a photograph of herself on the front page of the newspaper, the photograph associated with a hippie love-in where a riot occurred. Apparently, she was arrested. As Samantha knows it wasn't her, it could only be one other person: Serena. Samantha can hide the photograph from Darrin, but she can't hide it from the rest of the world, including Larry and Louise, who do see the photograph and naturally assume it's Samantha, despite she being the furthest thing from a hippie. When Darrin finally learns about the photograph, he is livid and banishes Serena from ever entering their house again. Angry in return, Serena decides the best way to get back at Darrin is to create havoc in his life by pretending to be "hippie" Samantha in front of Darrin and Darrin's colleagues. Serena's action results in McMann & Tate losing a conservative client, but Larry is more concerned about Darrin and what's happened to Samantha. The only way that Darrin can prove to Larry that the woman he saw was Serena is to provide both Samantha and Serena together. But with Serena still mad at Darrin, it's not like she will willingly do him a favor.
—Huggo