Which actor plays Robert Graysmith in Fincher's Zodiac?

Jake Gyllenhaal plays political cartoonist Robert Graysmith in David Fincher's Zodiac.

The 2007 crime thriller follows the investigation into the Zodiac Killer, who terrorized the San Francisco Bay Area in the late 1960s and early 1970s. Graysmith was a cartoonist at the San Francisco Chronicle who became deeply interested in the killer's letters, ciphers, and identity.

Gyllenhaal's performance traces Graysmith's transformation from a curious newspaper employee into an obsessive amateur investigator. The film is based on Graysmith's books Zodiac and Zodiac Unmasked, though it dramatizes events and does not establish every conclusion as definitive.

The other major investigators are played by Mark Ruffalo as San Francisco detective David Toschi and Anthony Edwards as Inspector William Armstrong. Robert Downey Jr. plays crime reporter Paul Avery. Because all three men pursue the case in different ways, viewers can sometimes confuse their roles, but Gyllenhaal is the actor portraying Graysmith.