Owner/Moderator e-mail bouncing. How might I the moderator of this group?

I am a member of a members only group that has recently seen alot of unsavory messges that have nothing to do with the content of the group. It seems our group owner/moderator is no longer available, their e-mails are bounding. I'd like to clean up the goup and get it back on track. So how do I do that?