Smallville, Season 4

Chloe:
So, popular question of the day. What is Clark Kent's worst nightmare?

Clark:
When I woke up. Everyone that I knew was gone. I was completely alone.

Chloe:
I wish I could say that I'll always be there for you, but somehow I get the feeling that may not be a promise I can keep. You were the only one who came out of it, Clark, and I don't think it's because you've been taking your vitamins... Look, you know what? You don't have to tell me. I know that I gave you my word that I was going to stop all this prying but... In these last few months, I really got a taste of what it was like to keep my mom's secret, and I've never felt more alone.

Clark:
It's weird when people think they're so close to you but have no idea what you're really going through.

Chloe:
Yeah. I'd hate to live my whole life like this. But after 'fessing up, it's amazing how quickly that feeling of loneliness disappears. I mean, if you can't tell your best friend, who can you tell? Right, Clark?