Question: Disappearance of Renee MacRae, Britain's longest running missing persons case, is as notorious as the murder cases of this serial killer involved with how many people? 
Context: Beverly Rose Potts (born April 15, 1941) was an American girl from Cleveland, Ohio, who in 1951 became the subject of a famous missing persons case when she disappeared only a few blocks from her home, after attending a show in a nearby park.  She has never been found and her disappearance remains unsolved. Unreported missing (also known as Missing Missing or Kids off the Grid) describes persons who cannot be found, yet have not been or cannot be reported as missing persons to law enforcement, specifically the National Crime Information Center database of missing persons in the United States.  The term applies whether the missing person is a child or an adult. The International Commission on Missing Persons (ICMP) is an intergovernmental organization that addresses the issue of persons missing as a result of armed conflicts, violations of human rights, and natural disasters.  It is headquartered in The Hague, The Netherlands.  It assists governments in the exhumation of mass graves and DNA identification of missing persons, provides support to family associations of missing persons, and assists in creating strategies and institutions to search for missing persons.  In December 2014, a treaty was signed which established the commission as an "International Organisation in its own right", which has 5 signatories, but has not entered into force.  The treaty designates The Hague (Netherlands) as the seat of the organization. Bible John is the nickname of a serial killer who is believed to have murdered three young women after meeting them at the Barrowland Ballroom in Glasgow, Scotland, between 1968 and 1969.  The killer has never been identified although the known movements and modus operandi of convicted Glaswegian serial killer Peter Tobin suggests that he may have been behind the killings.  However, this has never been proven and the case remains unsolved. Missing persons is a generic term used in Pakistan to refer to the alleged ostensibly hundreds of persons in Pakistan who have been forcefully disappeared by the different security and law enforcement agencies.  According to Amina Masood Janjua, a human rights activist and chairperson of Defence of Human Rights Pakistan; a not for profit organization working against enforced disappearance there are more than 70,000 reported cases of enforced disappearance in Pakistan.  There are no formal allegations or charges against the persons thus forcefully disappeared. Farzana Majeed is a Baloch rights activist, general secretary of VBMP-Voice for Baloch Missing Persons, a non for-profit organisation working for the awareness of Baloch Missing persons in Balochistan.  Farzana Baloch is known for her struggle for the recovery of Baloch missing persons.  She started her campaign as an activist after her brother Zakir Majeed - a former leader of Baloch Students Organization - Wikipedia, was abducted in 2009. The disappearance of Trevaline Evans is a missing persons case from 1990, concerning a 52-year-old woman who vanished without trace from her antiques shop in Llangollen, Denbighshire, Wales, United Kingdom. Special Agent Vivian "Viv" Johnson is a fictional character played by British actress Marianne Jean-Baptiste on the CBS TV drama "Without a Trace".  Vivian is second in command of the FBI missing persons case squad in New York City.  The squad solves a new missing persons case every week. The murder of Gerd Johansson is one of Sweden's most notorious murder cases, concerning the disappearance and murder of a 10-year-old schoolgirl in Stockholm on 1 December 1939.  Eight days after her parents had reported her missing her body was discovered in Lötsjön in Sundbyberg; she had been raped and strangled to death.  News media was filled with reports of the murder and her playmate Jan Sparring was interviewed by several media; Sparring later became a known singer in Sweden.  A month after her body was discovered, media reported that her killer must have a dog and that jute fibers had been found on her coat.  Police also stated that they were searching for a black car in connection with her murder. Renee MacRae (born Christina Catherine MacDonald, February 1940) is a Scottish woman who is missing, presumed to have been murdered.  Her disappearance along with her son is currently Britain's longest running missing persons case, and in Scotland the case is as notorious as Glasgow's Bible John murders.  Nobody was charged with the murders, and the case has remained open.
Answer: three