With its unhurried pace and cerebrally engaging plot, Zodiac is an unusually haunting and compelling horror film.
——Claudia Puig, USA Today
A film that is both emotionally and intellectually unsettling.
——Colin Covert, Minneapolis Star Tribune
This was a really good film. I was on the edge of my seat and the fact that it's a true story is an even more scary thought. All of the cast were exceptional.
The film opens on July 4, 1969, with the Zodiac killer's second attack, the shooting of Darlene Ferrin（Ciara Hughes）and Mike Mageau（Lee Norris）at a lovers' lane in Vallejo, California. Mageau survives while Ferrin dies from her injuries.
One month later, a letter written by the Zodiac arrives at the San Francisco Chronicle. Paul Avery（Robert Downey, Jr.）is a Chronicle crime reporter. Robert Graysmith（Jake Gyllenhaal）is a political cartoonist there. The newspaper receives encrypted letters that the killer sends, taunting the police. Because of Graysmith's status as a cartoonist, he is not taken seriously by Avery and the editors and is excluded from the initial details about the killings despite his interest in the case. In particular, he is drawn to the encrypted code that is included with the letters and is given access to one. When he is able to crack one of the codes and makes several correct guesses about the killer's actions, Avery begins sharing information with him. While at a bar together drinking Aqua Velvas, which Avery initially makes fun of Graysmith, they discuss the coded letters.
The Zodiac killer attacks again, stabbing Bryan Hartnell（Patrick Scott Lewis）and Cecelia Shepard（Pell James）at Lake Berryessa in Napa County. Shepard dies as a result of the attack, while Hartnell survives. Soon afterward, San Francisco taxicab driver Paul Stine is shot and killed in the city's Presidio Heights district. San Francisco police detectives Dave Toschi（Mark Ruffalo）and his partner Bill Armstrong（Anthony Edwards）are assigned to the case, liaising with other detectives such as Jack Mulanax（Elias Koteas）in Vallejo and Ken Narlow（Donal Logue）in Napa. The killer, or someone posing as him, continues to toy with authorities by speaking on the phone with celebrity lawyer Melvin Belli（Brian Cox）when he makes an appearance on a television talk show. Avery and Graysmith form an alliance, delving deeper into the case.
In 1971, Toschi, Armstrong and Mulanax question Arthur Leigh Allen（John Carroll Lynch）, a potential suspect in the case. However, a handwriting expert（Philip Baker Hall）insists that Allen did not write the Zodiac letters. Avery receives a new letter threatening his life. He becomes increasingly paranoid and turns to drugs and alcohol. At one point he shares information with a rival police force, angering Toschi and Armstrong.
By 1975, Avery leaves the Chronicle. Armstrong quits the homicide division, and Toschi is demoted for supposedly forging a Zodiac letter. Graysmith, meanwhile, continues his own in-depth investigation, interviewing witnesses and police detectives involved in the case. Obsessing over the unsolved case, he begins receiving anonymous phone calls with heavy breathing（on the night of Ferrin's death, Graysmith discovered that someone prank-called the victim's family and did the same thing）, Because of his submersion in the case, Graysmith loses his job and his wife Melanie（Chloe Sevigny）leaves him, taking their children with her.
Graysmith persistently contacts Toschi about the Zodiac murders and eventually impresses the veteran detective with his knowledge of the case. While Toschi cannot directly give Graysmith access to the information he discovered over the years, he provides contacts of other police departments in counties where the other murders occinred, The cartoonist acquires more information that points to Allen as the Zodiac, and although circumstantial evidence seems to indicate his guilt, the hard evidence, such as fingerprints and handwriting samples, exonerate him.
In December 1983, a full 14 years after the original slayings, Graysmith tracks Allen down to a Vallejo hardware store, where he is employed as a sales clerk. After Allen asks if he can help Graysmith with anything, they stare at each other for a moment with blank expressions before Graysmith simply replies with a “No”，and leaves the hardware store.
Eight years later, in 1991, Mageau（Jimmi Simpson）meets with authorities and identifies Allen from a police mugshot.
Final title cards, however, inform the audience that Allen died in 1992 before he could be questioned further by police, and that DNA tests performed in 2002 did not match samples gathered from the Zodiac letters.
Chloe Sevigny Interviewed by Paul Fischer
You don't do these kinds of big movies very often, if at all, and so first of all what did you think you could do with this character when it was offered to you?
I agreed to do the movie not so much as a character as just more so to serve the greater good of the movie and to work with David Fincher, because I think that he has a very distinct vision amongst all of these kinds of mediocre filmmakers working today in the business. Then I thought the character was interesting in that she's not this kind of girly girl but she's very practical, smart and kind of tough with her husband and I like that about her in that aspect of their relationship. Also she was very respectful of him and kind of let him run his course with this whole Zodiac mess that he had gotten himself into.
Now I mean in your case you didn't really need to do any research on this because I assume that in terms of your character，it's pretty much what's on the page. Did you allow yourself to do anything, did you meet with the real character?
I read most of Zodiac Unmasked. I didn't get through it because I found all of the insane detailing into all of the investigations just a little too much for my taste and a little hard to get through and the violence was definitely hard for me to read. It was very disturbing and I met with the real wife of Robert Graysmith. She came to the set with her daughter, briefly. But we didn't really get too in depth into their relationship or her life or anything.