The Stark advisor, Maester Luwin, comes to tell Catelyn and Eddard that he found a secret note in his room. It turns out that this note is from Catelyn's sister Lysa, who was married to Jon Arryn (confused yet?); the note says that the Lannisters poisoned Jon Arryn.
What's funny here is that this further convinces Catelyn that Eddard has to take the job: they killed the previous guy, so why don't you try that job out?
Now, we love Catelyn, but one thing that we don't get is how much she hates Jon Snow. She tells Eddard that Jon Snow can't stay when Eddard goes to King's Landing, but Eddard can't bring him to the capital.
Luckily, Luwin has the solution: let Jon Snow join the Night's Watch.
(Okay, by this point, you are absolutely confused by these zillion and a half characters. It only gets more confusing, so here's where we at Shmoop tell you: just go read the book! Use our summary as a refresher, but if you haven't read the book, well… good luck.)