Family Guy: Season 14, Episode 17

14 - 17: Take a Letter

To pay for Stewie's private school, Lois becomes a postal worker. She finds a letter from Peter that was never sent to his old fling, Gretchen (guest voice Kathryn Hahn), dated a week before their marriage. When Gretchen tries to come between Lois and Peter, Lois has a plan of her own.