Martin receives a letter from his cousin Gaylord Lane (George Gaynes) asking if his daughter Betsy (Patty Duke in her third role in the episode) can stay with them for a little while. The platinum blonde Southern doll grabs the boys' attention. Cathy's boyfriend George (Jeff Siggins) falls for her and takes her on a date she disapproves of- to a western movie. Cathy doesn't tell Betsy that George is her boyfriend. Richard is next in line and afterward Patty does inform an apologetic Betsy. Betsy begins to like living there and wishes for it to be permanent. She realizes she can't as long as Cathy is living there and conspires to make her want to move. Betsy works to manipulate Patty and Cathy to resent one another and drive them apart. They see through the scheme and wish to react in anger, but Martin wishes to know the root of Betsy's problem.
I feel Patty Duke did a tremendous job convincing viewers that Patty and Cathy are two different people. You really buy into the separate characters. But three... not here. I felt it wasn't until halfway into the episode that she began feeling more comfortable in the third role. The moral attempt here was fine, but the story seemed to come a little easy in my opinion.