OK, it's crazy, I know, but I think Lundy is really the Trinity Killer. Follow me here - first, notice how completely odd it was that suddenly Lundy is wearing a hat that makes him look like Hannibal Lecter? Secondly...Lundy and John Lithgow's character bear a strong resemblance to one another. Lastly - remember Lundy said in the last episode that he'd been married for 29 years? And the initial Trinity Killer murders ocurred 30 years ago, BEFORE he got married? And now that Lundy is retired, what a coincidence - the murders start up again.
I wouldn't be the least bit surprised if at the end of this season, we learn that the Trinity Killer is Lundy's alter-ego. You heard it here first!