Netflix has launched another true crime documentary based on one of the most notorious crime mysteries to ever riddle France.
Who Killed Little Gregory?, which dropped on November 20, delves deep into the unsolved murder of four-year-old Gregory Villemin.
The young child's body was found on October 16, 1984, tied up and drowned in the Vologne river in an area of eastern France close to the Vosges mountains.
The show's description reads: "When their 4-year-old son is murdered, a young couple fights a twisting and arduous battle trying to identify a frustratingly elusive killer."
Nobody had ever been convicted of the killing. This is the true story behind the murder of Gregory Villemin:
What was the background to the case of Little Gregory?
The case of Little Gregory, as it was known, became one of France's most notorious post-war criminal mysteries as police sought to untangle a web of family hatreds and local jealousies.
Since 1981 the child's parents had been receiving anonymous phone calls and hate mail from someone calling himself "Le Corbeau", or the crow.
Not only was this person threatening revenge against the family, specifically the child's father Jean-Marie, but they also had intimate knowledge of the extended family.
What happened to Little Gregory?
On October 16, 1984, Jean-Marie and his wife Christine reported to police that their son was missing. Shortly after this, at 5pm the same day the boy's uncle received an anonymous phone call telling him the boy had been kidnapped and dumped in the Vologne River.
The young boy was found tied up and drowned in the Vologne river in a bleak area of the Vosges mountains in eastern France.
His hands and feet were bound with rope and his face covered with a wool hat.
A day after the body was found, a poison-pen letter arrived at the home of the child's parents claiming responsibility for the murder and calling it "vengeance".
The killing set in motion a chilling crime saga that has kept France gripped for the past 30 years.
What happened afterward the murder of Little Gregory?
A second cousin of the child, Bernard Laroche, was charged with the killing, based on evidence given by his 15-year-old sister-in-law Murielle Bolle - but was released from custody after she withdrew her allegations, claiming she had been pressured by police.
The authorities then came up with a new theory, that his mother Christine was the killer.
The pregnant woman collapsed after questioning and was taken to hospital, reportedly losing one of the twins she was carrying.
Between hospital visits, Gregory's father Jean-Marie went to Laroche's home and shot him dead.
Villemin was sentenced to five years in prison for the crime.
Later that year, his wife was charged with her son's murder. Christine was finally cleared eight years later and all charges against her dropped.
The inquiry was reopened briefly in 2000 to allow for DNA testing of a stamp on a hate letter sent to the Villemins months before the murder.
But it was closed in 2001, after the probe failed to yield any clues as to the identity of either the killer or the sender of the mysterious letters.
In December 2008, the parents fought to have the case reopened so that DNA testing could be carried out on the rope used to tie their son's hands and feet, as well as letters and other evidence.
But again it proved inconclusive, with further DNA testing in April 2013 on the boy's clothes and shoes also providing no clues.
In June 2017, Bolle was also arrested on suspicion of involvement in the killing, but was later released. That same month, three other members of the child's extended family were also arrested.
The following month Jean-Michel Lambert, who was the investigating magistrate in charge of the first administration, committed suicide. In a suicide note he said he feared that reopening the case would discredit his own findings years earlier.
The killer is still yet to be found.
