TIMELINE: How the double murder unfolded over 25 years
More than 20 years after Robert Grayson and Derek Van Van Der Poel were last seen, the mystery could be over.
Today Russell Williams, a 51-year-old Rosedale man, is expected to front court on two charges of murder and one count of drug production, in relation to the long-running investigation.
Here is how it has unfolded:
May 1993 - Robert Grayson and Derek Van Der Poel last seen alive in Gladstone.
Late May 1993 - Robert Grayson and Derek Van Der Poel are dropped off in Kroombit Tops National Park near the location of the cannabis crop they were tending to.
May/June 1993 - Alleged murder of Robert Grayson and Derek Van Der Poel occurs.
June 1993 - Persons responsible for the cannabis crop realise Robert Grayson and Derek Van Der Poel are missing but fail to report it to police.
August 8, 1994 - Robert Grayson reported missing.
September 2, 1994 - Mrs Jean Fisher files a missing persons report with Calliope Police in relation to her grandson Robert Grayson.
September 4, 1994 - Grayson's companion Derek Van Der Poel reported as missing.
Late February 1995 - Detectives search the Kroombit Tops crop location, finding an abandoned campsite believed to have been used by the men.
August 7, 2004 - A $100,000 reward is posted by police for any information that could lead to the apprehension of persons responsible for the disappearance and suspected murder of Robert Grayson and Derek Van Der Poel .
December 3, 2004 - Police and Corrective Services Minister Judy Spence increases reward to $250,000.
May 4, 2006 - Police reveal a witness has come forward in relation to the murders of Robert Grayson and Derek Van Der Poel.
May 11, 2006 - An anonymous male caller provides police with information in relation to the murders of both men.
May 12, 2006 - Police appeal to the anonymous caller to contact them again in relation to the crucial information he earlier provided.
August 7, 2007 - Police renew appeal as part of National Missing Persons' Week.
January 29, 2018 - Man arrested and charged.