'Joker' toes fine line in portraying the making of a monster

"Joker" might bring to mind a caped crusader, but it's another vigilante, "Taxi Driver's" Travis Bickle, who provides the movie's spiritual sire. Joaquin Phoenix's electric, disturbing performance is thus dogged by history and questions about the "why" of it all -- that is, a Joker without Batman -- an answer that isn't really in the cards.