Watchmen is reduced to a two-character cat-and-mouse game between a nosferatu-esque Ozymandias and a...nosferatu-esque Rorschach.
Bruce Wayne, in his dotage, has finally gone off the deep end and is checked into a mental institution. He engages in several humorous and nostalgic battles of, um, "wits" with his former enemies, all now too old to cause any real trouble beyond the accidental death of the occasional orderly. Perhaps they team up to take over Arkham. Perhaps they just masturbate a lot. You can never tell with Moore.
Incidentally, if you haven't seen this it's worth a read; Stan Lee's The Watchmen