This isn't really a spoiler, but I suggest to anyone who hasn't read the books to go back and watch the Walder Frey episodes, where Robb Stark promised to marry his daughter to gain passage.
He needs his help again, but married someone else, and in the last episode they didn't really play up the consequences very well.. he was like "we need them but err I was supposed to marry his daughter lol oops"
You should know what kind of person Walder Frey is, so go back and watch that episode to remind yourself
