Well, for those who haven't gotten to season 5 yet, anyhow!
I've been catching up on old episodes, and I'm trying to find out which episode it was that Clark finds out that Chloe knows his secret.. I'm thinking it almost had to be in the season premiere of episode 5?
Now, just to make sure, I know when she finds out, but I'm trying to figure out when HE finds out she knows..
I forget the name of the episode. But it is the season 4 season finale I think. Or the first episode of season 5
Clark finally reunites the stones, goes to Jor-el who transports him to the north pole. Clark throws the stone and it begins to create the fortress of solitude. Lex drags Chloe to the caves, she knocks him out and goes after Clark. She uses the key to follow him to the north pole. Only she had no idea what was going to happen. (And didn't bring her parka) She almost freezes to death in the fortress, then tells Clark she knows he can move faster than a speeding bullet and asks him to super speed her out of there.
Does that help?