Zodiac stands as director David Fincher's most impressive monolith to date, a sprawling, three-decade-spanning infodump that, for all its virtuosity, occasionally feels like being locked in the file cabinet of a conspiracy junkie. James Vanderbilt's script follows the obsessive, dogged attempts of editorial cartoonist Graysmith (Jake Gyllenhaal) and police inspector David Toschi (Mark Ruffalo) to uncover the identity of Northern California's notorious (and media-savvy) Zodiac killer. Rather surprisingly, the actual murders are dealt with in a few early scenes, leaving the lion's share of the 150-minute running time to exploring seemingly every slim theory ever generated on the subject. Thank the cosmos for the presence of Robert Downey Jr., whose supporting turn as San Francisco Chronicle reporter Paul Avery consistently finds ways to jump out of the film's predetermined groove.