When Ted's younger sister, Heather, comes to visit and decides she wants to move there, Ted worries that she's not mature or responsible enough to survive in NYC. Being the overprotective older brother, Ted tries to keep her out of trouble, and in particular keep her away from Barney. But when Ted becomes too overbearing, Heather teaches him a lesson that gives him new respect for her. And after northern natives Marshall and Robin bond during the first frost of the year, Marshall helps Robin get through her worst bout of homesickness by introducing her to his favorite Minnesota themed bar.