Robb and company arrive at the Twins. Robb nearly upsets the Freys when his wolf scares Petyr Frey's horse, but things get smoothed over.
In fact everything goes very smoothly. Robb does not get angry when old Walder Frey makes jokes at his expense, or makes him apologise to his daughters. Even Edmure seems happy with his bride. Catelyn worries about her hips, but the maester reassures her that her mother had the same hips and had lots of children.
Old Walder Frey, dirty old man that he is, jokes that Edmure can't see his bride naked until after the wedding. I'm fairly sure that even in Westeros husbands to be don't make such thorough inspections as a matter of course. So this seems an odd thing to say.
And everything is going so well. Suspiciously well. Even the rooms they are staying in are nice, and these are the miserly Freys. Something is up. I'm betting that young Roslin Frey has a secret. And I'm betting: she's a hermaphrodite! Yes, that's my theory and I am sticking to it until proven otherwise.