Cindy is feeling like a little kid around Marcia and Jan, who are going on dates and getting dressed up. Cindy wants to do all those things her older sisters are doing and tries to act older in an effort to get what she wants. Cindy's new mature attitude seems to be noticed by someone as she ends up getting a secret admirer, who is sending her notes and presents. Mike eventually catches her secret admirer delivering Cindy's latest gift, he who ends up being not who Mike and Carol expect. Despite a talk Mike and Carol have with the secret admirer to tell Cindy certain things, Cindy eventually does meet the person she believes is her secret admirer - who in reality isn't that same person - and learns that acting grown up does have its disadvantages. Her real secret admirer, however, still has to face the music.
—Huggo