That was devastating. Generally speaking the changes the show makes to the source material are problematic; the handling of the Robb/Catelyn storyline since the end of season one is the biggest example. But the invented stuff here-- Bolton and Catelyn, Arya and Grey Wind, Talisa-- was very visually effective. And gosh, Michelle Fairley is extraordinary. The failure to properly set up the Freys and the Boltons over the course of the season turns out not to matter much, at least on a visceral level.