Between 1968 and 1983, a San Francisco cartoonist becomes an amateur detective obsessed with tracking down the Zodiac Killer, an unidentified individual who terrorizes Northern California with a killing spree.

When two girls disappear into the woods and return three days later with no memory of what happened to them, the father of one girl seeks out Chris MacNeil, who's been forever altered by what happened to her daughter fifty years ago.

Four detectives in four different time periods of London find themselves investigating the same murder.