Making The Misfits the rangy Western Arthur Miller wrote for then wife Marilyn Monroe ended the playwright's marriage and his innocence 44 years ago. Now, Miller elevates that incident to myth, with results both transfixing and preposterous. Cartoon versions of Misfits director John Huston (Harris Yulin), Miller himself (Matthew Modine), and hated ''Method'' Svengalis Lee and Paula Strasberg (Stephen Lang and Linda Lavin, so good they make defamatory caricature look artistically responsible) roam vast, hotel-suite wastes, intoning nebulous notions of exploitation and endemic guilt a scrapbook of vintage Miller themes. Yet Finishing the Picture doesn't feel like a summing-up, just high-blown belly-aching, directed at manic movie star Kitty, whose voice we hear only in brief shrieks and mumbles. It's a fascinating mess treated as comic passion play, which explains why Scott Glenn has the most fun, embodying a boorish cinematographer with a buttock-based theory of film. The play at large could have benefited from his limber unselfconsciousness.