It could be argued that it would be rather meaningless for the sadistic caller to threaten a woman in a blue house, had this woman got no connection whatsoever to Daniel Williams. The caller was clearly targeting Daniel Williams and attempting to unnerve him. When Daniel Williams left his house on November 2nd 1969, the killer gained access by prying open his screen door and placing some arsenic in his soft drink. There is every chance that the perpetrator had followed Daniel Williams to some extent and was aware of his departure from his Martinez home that day. Had this person also seen Daniel Williams visit or converse with a woman in a blue house, possibly on Bush Street where he lived - and knowing that he was friendly with this woman - he knew that a threat to kill her would resonate with the school teacher? Threatening an unknown woman to Daniel Williams, plucked from nothing more than his imagination, appears rather pointless. However, there is a more unlikely alternative.
The next possible letter by the Zodiac Killer arrived at the San Jose Police Department on November 21st 1969, threatening a woman and accompanied by the wording "There's no doubt I will do my Thing!". In the Dripping Pen card the Zodiac Killer wrote "I though you would nead a good laugh before you hear the bad news. You won't get the news for a while yet. PS could you print this new cipher in your frunt page? I get aufully lonely when I am ignored, so lonely I could do my Thing !!!!!! Des July Aug Sept Oct = 7". Was the communication on November 21st 1969 the bad news he had promised us, and the culmination of the threat to "kill the lady in the blue house". In this communication the author threatened a widow, with enough detail in the letter that police were able to identify her. They took the threat extremely seriously, instituting 24-hour surveillance on her and her property. It is impossible, fifty-one years after the fact, to establish whether any connection exists between this woman and Daniel Williams. The likelihood of a connection is extremely remote, but it would have been interesting to find out the color of her house.