Melissa's annoying, hoity-toity sister, Debra, tries to fix her up via two tickets to the Periodontists' Ball. One for her and one for Murray Lieberman, a dentist who works in the same office as Debra's husband, Len. Melissa hates blind dates (and her sister) and doesn't want to commit to an evening with someone she hasn't seen. Tracy and Georgy convince her to make an appointment with Murray, so he can check out her gums... and she can check out him. Melissa finds Murray so attractive that she puts aside her reservations and invites him to the ball, just like Debra wanted. Unfortunately, Murray already has a girlfriend, and is going with her -- and Melissa needs to have a plaque scraping. Melissa assumes that Murray's nurse, Shannon, is his girlfriend, but when she makes small talk with Shannon, she finds out some good gossip to destroy her sister with: Shannon is having an affair with Len. Tracy and Georgy talk Melissa out of laughing about it to Debra, but now Melissa has to go to t