How to retrieve Dialog responses from within a plugin?

I am looking for a way to retrieve dialog responses from within a plugin in CRM 2011 Online.  What I want to do is run a Dialog from a Contact, gather some information within the dialog, and then on completion of the dialog, kick off a plugin to do some processing based on the responses within the dialog.  I was able to register the plugin on an Update of a Dialog, and it should be able to check when the dialog status has changed to completed, but I don't see where within the processsession entity I can get the responses.  Are the dialog responses part of a different entity?  Thanks.