The Other Side, detailed James Pike's attempts to contact his dead son in the afterlife, described "as a moving narrative of a father's efforts to save his son from enslavement to psychedelic drugs, a tragic story of a young and gifted man's premature death, a startling story of poltergeist occurrences that led the father and other witnesses to believe that from beyond the grave his son was trying to get in touch, and a detailed account of how this communication proceeded during a time when the father was under accusation for heresy for believing too little".
She became Diane Kennedy Pike, an American writer and educator who lived in San Jose at the time this threatening letter was mailed. She was a school teacher at Willow Glen High School in San Jose between 1962 and 1964. It has been argued on this website that the Zodiac Killer made persistent threats on school teacher Daniel Williams, by way of threatening phone calls to his residence in Martinez and subtle references in the Zodiac Killer's two previous November communications, starting on October 23rd 1969 and ending on November 9th 1969.
Having recently become a widow after the tragic death of her husband in Israel in September 1969, Diane Kennedy Pike was featured in many newspaper articles in the intervening period before the November 21st 1969 "Zodiac" letter arrived. In August 1969, Pike and Diane traveled to Israel, to do research for a proposed book on the historical Jesus. They attempted to travel to Qumran but during their journey through the Judean Desert they got stuck in a deep rut on a dirt road. After leaving the vehicle they went in search of help, with Diane ultimately separating from her older husband (who was in a serious condition). She eventually found help and a rescue party began the search. Unfortunately, it came too late for James Pike, who was found deceased five days later on September 7th 1969. By targeting this widow in San Jose (because of her history and connections), the Zodiac Killer may have thought this would secure him more front page coverage. However, this communication seemingly fell by the wayside - and as of writing - no newspaper coverage of this threat has been uncovered. The Other Side, featuring the afterlife, by the high profile authors of Diane and James Pike, along with his recent death in Israel and the publicity that surrounded it, may have been the required incentive for the Zodiac Killer to threaten this widow in San Jose on November 21st 1969. But until the FBI file is unredacted, we will never know for sure.