goldman wrote the original novel while experiencing writer's block, when writing "boys and girls together" (published in 1964). he was inspired by an article about the boston strangler which suggested there might be two stranglers operating, and goldman wondered what would happen if that were the case and they got jealous of each other. (in the film adaptation, there is only one strangler; goldman hated this change.) he says as he walked to his office, "the book simply jumped into my head. start to finish. the whole thing... and i remember getting to my office and frantically scribbling down an enormous number of chapters." goldman was worried about never finishing "boys and girls together", so he gave himself two weeks to write the new novel.