Everything is set for Susan and Karl's remarriage of convenience, except for a ring. Karl wants her to use the one he originally gave her, since it was a family heirloom, but she admits she threw it out her car window the night he left her for another woman. So he takes her back to the scene of the crime and makes her hunt for it with a metal detector.
Edie comes across the ring in Karl's briefcase, right next to a prenup, so, since it's Valentine's Day, she assumes he's going to pop the question that night at dinner. Edie and Karl and Susan and Dr. Ron both happen to be dining at the same restaurant, so Edie takes Susan aside and brags that Karl's about to propose. When Susan gently tries to explain everything away -- maybe Karl was just having the ring cleaned and the prenup's for a client? -- Edie accuses her of being jealous.