Disappearance of Mona Blades

Mona Elizabeth Blades was an 18-year-old New Zealand woman who disappeared on 31 May 1975 while hitchhiking from Hamilton to Hastings, on the first day of the Queen's Birthday long weekend. She was allegedly last seen on the Napier–Taupo Road getting into an orange Datsun 120Y station wagon, according to a truck driver's report. Other witnesses reported seeing a matching vehicle veering off the highway and stopping on rural Matea Road. Blades' body and belongings have never been found.

Following her disappearance, police spent thousands of hours interviewing New Zealand's more than 500 orange Datsun owners in an effort to trace the vehicle reportedly involved. Auckland police investigated a man who had rented an orange Datsun the same weekend Blades disappeared; on the day police publicly announced they were searching for an orange Datsun, that man shot and wounded a student at St Cuthbert's College in Auckland before killing himself.

Over the following decades, several other individuals were identified by police as "persons of interest," including an elderly New Zealand man and a Hamilton man, Charlie Hughes, who later moved to Australia. Hughes has publicly denied any involvement in Blades' disappearance and has spoken to media about the impact of remaining on the suspects list. In 2003, police investigated a report that Blades' name had been found etched into a garage floor in a Huntly house, raising fears it might mark a makeshift grave; it was later determined the inscription had been made as a joke six years earlier, and the former property owner apologised to Blades' family.

In 2005, Blades' brother Tony Blades told the Daily Post that the family had avoided speaking to media for three decades because of the emotional toll, particularly on their mother, then in her 80s; their father had died without learning what happened to his daughter. A former Kawerau police officer later alleged that a former colleague, a traffic officer, had been involved in Blades' death — allegations that were strongly rejected by the former colleague's family. Based on these allegations, police used excavators in January 2012 to dig up the laundry floor of a Kawerau property where the former traffic officer had lived in the 1970s, but found nothing of interest.

The case was revisited in July 2018 on TVNZ's Cold Case programme, in which detectives re-examined the original investigation files. Experts concluded the original inquiry had focused too heavily on the orange Datsun and may have misled witnesses through use of photographs that did not resemble Blades' hairstyle at the time of her disappearance. A detective involved in the review suggested gang members or their associates may have been connected to the disappearance, noting Blades had gang affiliations and that gang members may have been travelling the same road toward a gathering in Wellington that weekend. As of the available sources, the case remains unsolved and no one has been charged.