Eddard Stark offered her a deal. Safe return to the Seven Kingdoms but in exchange she would need to marry his son, to keep her under watch instead of killing her like Robert wanted. She accepted because she believed she could work on her plans from within. She could turn the Young Wolf in her ally. But she wasn't expecting Robb Stark not to be like the men she knew.

AU. Tyrion's escape plan for Jaime is successful, and he leaves Riverrun without having made a vow to return Catelyn Stark's daughters. He arrives immediately after the Battle of Blackwater and learns the truth about Cersei much sooner. Joffrey and Sansa are still engaged. How will his presence change events? Slightly Older Sansa/SPOILERS for books & upcoming seasons