The Chamber was opened before and they thought Hagrid did it?? That can't possibly be right!...well...not on purpose that is!
You run downstairs, 3 steps at the time, and find Ron still sitting at the fireplace lazily throwing a toy sized quaffle up in the air, 'Oh I'm studying, I'm studying!' he starts, jumping up and pretending to be writing on his half empty parchment. Then he sighs and melts back on the sofa once he sees it's you and not Hermione. Before he gets too comfortable, however, you grab him by his sleeve and shout I'll explain on the way.
You have the sense to grab the invisibility cloak, as it's way past curfew time, and sneak out of the castle to go and see Hagrid. Somehow this does not feel like something that can wait till morning.
He seems like he was expecting you to come over with this exact question. He's about to explain everything, but the Minister of Magic, of all people, barges in. You can barely contain your rage underneath the cloak, hiding in the corner, when the Minister almost spells it out that they are only taking Hagrid to Azkaban, the wizards prison, to appear as if they're taking action against the attacks in publics eye, even when they don't truly think Hagrid is responsible.
Just before Hagrid is led away, he says:
"If anyone wanted ter find out some stuff, all they'd have ter do would be ter follow the spiders."