Family Guy - Season 14 Episode 17 Take a Letter Parental Discretion Advised, that's how you know it's good.
Overview: 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, dated a week before their marriage. When Gretchen tries to come between Lois and Peter, Lois has a plan of her own.