Comments with milti-level discussion

Hi

I’m sorry if this is already widely covered in this forum.

I’m running an older theme on my WP blog and are looking for an easy to set up plugin that will allow multi-level discussions in the comments. My current theme only have the old one comment level and there’s no way for pleople to respond to that comment other than posting a new comment. I see that most blogs today have reply links underneath each comment allowing further discussion to specific comments. Sorry for my clumsy description.

Any help is much appreciated! Thanks!