According to Variety, Robert Downey Jr., Jake Gyllenhaal and Mark Ruffalo will topline serial-killer thriller Zodiac, the Paramount and Warner Bros. co-production to be helmed by David Fincher.

Production is slated to start in mid-August, with Phoenix Pictures producing. Scribe Jamie Vanderbilt is adapting from Robert Graysmith's 1986 true-crime tome "Zodiac" and 2002 sequel "Zodiac Unmasked: The Identity of America's Most Elusive Serial Killer Revealed."

Fincher and his partner Cean Chaffin are producing with Vanderbilt and Phoenix principals Mike Medavoy, Arnold Messer and Brad Fischer.

Gyllenhaal will portray Graysmith, a San Francisco Chronicle cartoonist who began tracking the mystery of the serial killer. The Zodiac terrorized the San Francisco area from 1966-78, committing at least 37 murders and documenting his exploits in taunting letters sent to the Chronicle.

Graysmith believes he identified the killer, but competing investigations and other circumstances prevented the suspect, who died in 1992, from ever being apprehended.

Ruffalo will portray the lead investigator in the case, Downey a reporter.

Downey's toplining in Warner's Kiss Kiss Bang Bang, Shaggy Dog and Fur with Nicole Kidman. Gyllenhaal will next appear in Jarhead, Proof and Brokeback Mountain, while Ruffalo will be seen next in All the King's Men, Rumor Has It and Just Like Heaven.