An ordinary suburban family is shattered when their youngest son is killed in an accidental fire while locked inside the family's car on their yard. Mother Marja can't stop crying, father Jaakko can't cry at all but blames himself for the fire. Their remaining son Timo develops problems at school because of his constant worries about his parents' safety. In their grief, Marja and her sister Leena have to confront an old family secret, their little sister's accidental death for which Leena has quietly blamed herself through decades.
High school best buddies are facing separation anxiety as they prepare to go off to college. While attempting to score alcohol for a party with help from their fake ID-toting friend, "McLovin", the guys' evening takes a turn into chaotic territory.
Based on the actual case files for one of the most intriguing unsolved crimes in America, "Zodiac" tells the story of a serial killer that terrified the San Francisco Bay Area, taunting police with his ciphers and letters.