A San Francisco detective is obsessed with catching a serial killer who has been killing people for over 20 years. When the detective learns that he has only a few weeks of life left, he tries his one last shot - taking the suspect for a ride down memory lane, hoping to force him into a confession... Based on the never-solved case of the serial killer "Zodiac" from the 70's, a number of crimes supposedly committed by the Zodiac much later, and one modern hypothesis concerning the murderer.