I HAVE TO ADMIT IT, I WAS KIND OF UNDERWHELMED by last night's Law & Order. The plot wasn't ripped from the headlines; it was ripped from the Warner Bros.' film archive. It was just a cheap knock-off of "Strangers on a Train", as even the shows writers acknowledged in a throwaway line. The retirement of Lennie Briscoe was handled with subtlety - probably too much subtlety. One the one hand, it was nice, after what I'm told was the hyper-maudlin Friends finale, to see a show mark the end with some sense of understatement. On the other hand, Briscoe was a great character, who'd been part of my mental furniture for years. I would have appreciated a little more to-do.