Lissy takes a stand for the less popular kids in school when she decides to take a nerd to the Valentine's Day dance, and Ethel, whose Valentine date with Rudolph Valentino has fallen through, ends up as a date for the nerd's brother. Meanwhile, when Richard brings his new invention home -- a lie detector called the "Ball O' Truth" -- Lissy and Ethel are forced to say tell their geeky dates their true feelings.