Sessions in controller actions

I have a session variable that only appears in a certain controller’s
action. Is there something that relates session state to actoins?

e.g.
/member/list.rhtml
“<%= debug session %>” in page shows session[:return_to] is nil
Click on link to go to show

/member/show.rhtml
“<%= debug session %>” shows session[:return_to]'s prior value.

This is very strange to me. Am I missing something? Any suggestions
for debugging session issues in rails?

Thanks,
Nick

Nicholas Van W.