Someone is killing prostitutes, and the police are baffled. A prostitute who is a friend of Dan's is cautioned not to work but feeling that he already got his mark will strike so soon. At the police, a man named Phillip Grayson, an amateur criminologist, arrives who says that another prostitute will be killed before sunrise. And it was the one Dan spoke to earlier. He says that they are dealing with someone who is emulating Jack the Ripper, because each of the victims have the same name of the Ripper's victims. After stating that the Ripper's next killing will not take place for another month, they feel that they have time. But Grayson and Dan suspect that he may be losing touch with reality and will not wait for the month to carry out his next killing. Valerie, a policewoman and friend of Dan's, suspects the same thing so she sets herself as a prostitute with the name of the Ripper's next victim. Dan finds her and backs her up. What they don't know is that he is already there, hiding (thetvdb.com)