A shocking portrait of the world of a recently captured serial killer, who sees his killing of prostitutes as in accordance with Islamic teaching. Over the space of a year, 16 women were murdered in the Iranian city of Mashad. Because the victims were lured into the killer's traps, the press soon called these the "spider killings." All but one of the victims had previously been arrested for prostitution and drug-related crimes. When a 39-year-old contractor is arrested and confesses to the crimes, he claims divine support for his crimes. His mother, wife, son, and many neighbors agree. AND ALONG CAME A SPIDER visits with the families of the victims, with the perpetrator and his family, and with prostitutes in this holy city. Most chillingly, the killer's son proudly re-enacts a murder, and suggests that he wants to grow up to be like his father. This is a chilling film about cycles of moral vengeance.

影片男主角的原型是一位伊朗裔，加拿大籍的记者巴哈里（Maziar Bahari）。2009年，巴哈里作为美国《新闻周刊》（Newsweek）驻伊朗记者，报道当年的伊朗总统大选。6月13日，选举委员会宣布艾哈迈迪-内贾德（Mahmoud Ahmadinejad）获胜后，其竞争对手的支持者上街游行，巴哈里拍下了这场被称为“伊朗绿色革命”的抗议活动。6月21日，他从德黑兰的家中被带走，经历118天的监禁后获释。 其后巴哈里将自己的这段经历写成回忆录《Then They Came for Me》，于2011年出版。在书中，他描述自己遭到折磨和审讯，对方视他为潜入伊朗的间谍。由于双眼被蒙住，看不清提审人的面容，只闻到他身上的玫瑰香水味，巴哈里在书中就以“玫瑰香水”（Rosewater）称呼对方，影片的片名也是由此而来。