Shoot – the young knight that Gregor killed yesterday was Jon Arryn's ex-squire, Ser Hugh, with whom Eddard was hoping to talk.
Eddard talks Robert out of fighting in the melee and Robert complains about being king. (Tough life, we know.) Eddard also doesn't like that Robert's squires are both Lannisters, Cersei's nephews Tyrek and Lancel.
At the tournament, Ser Loras unseats Ser Gregor, who goes a bit insane: he tries to kill his horse, tries to kill Loras, and then tries to kill his brother. Fortunately, the people are safe. The horse, not so much.
Later that night, a disguised Varys sneaks in to see Eddard. Varys now trusts Eddard since he got Robert to not fight in the melee (which would involve, you guessed it, an assassination attempt). So Varys tells Eddard that someone poisoned Jon Arryn because he was asking too many questions. Yikes.