CONTENT WARNING: This article contains brief references to violence, murder, and suicide in one of the most compelling episodes of Netflix's new "Unsolved Mysteries" (opens in a new tab), in which a French investigator and friends retell the strange, tragic, and ultimately inexplicable story of the Dupont de Ligonnes family murder (opens in new tab) retells the strange, tragic, and ultimately puzzling story of the case (opens in new tab). The seemingly perfect family, aristocratic, strict Catholics, community members, and full of character, apparently harbored deep secrets that were only revealed after all but one of them were systematically executed in their sleep and buried under the house. Four members of the family (Agnes, Arthur, Anne, and Benoit) were killed between April 3 and April 5, and the fifth (Thomas) was killed some time later.

Friends and family were concerned about their sudden disappearance and asked the police to search several times before their bodies were found, but the investigation became bogged down when the missing patriarch, Xavier, wrote a lengthy letter explaining their disappearance and asking the family not to worry. Xavier became a prime suspect in the family's murder and has never been found, dead or alive. After the tragedy made national news, the family's financial troubles came to light, as well as reports of marital tension between Xavier and Agnes.

The family's oldest daughter worked at a Catholic school and, according to neighbors, was good-natured. She was also unhappy in her marriage and worried about financial problems, according to comments posted anonymously on a French medical website (open in new tab).

"Kindness, love, mutual friends, sex, everything is missing," she wrote.

"The father is the head, he gives orders, and we carry them out without question or understanding.

Several neighbors claimed to have seen Agnes after the day she supposedly died, but that has not been proven.

The oldest of their four children was not Xavier's biological son: Xavier and Agnes dated, broke up, and reunited when she became pregnant with another man. Xavier and Agnes dated, broke up, and were reunited when she became pregnant by another man. Xavier took the child as his own and gave Thomas his name (according to a friend in this episode, this was quite unusual in Xavier's conservative circles). Arthur was 20 years old at the time of his death and was pursuing a degree at a private Catholic university. In the photo below, he is lying and fooling around across other family members (Benoit, Anne, and Thomas), but Arthur apparently had a girlfriend, and when she stopped hearing from him, she became concerned and stopped showing up for work.

Eighteen-year-old Thomas, Xavier's oldest son, was shy, kind, and apparently obsessed with music. Testimony is divided as to when he was killed and why later than the rest of the family. According to an episode of "Unsolved Cases," Thomas was visiting a friend and was called to the house on Xavier's pretext that Agnes had been in an accident.

When Xavier and Thomas went out to a local restaurant for dinner on the evening of April 4, the rest of the family was supposedly already dead, but according to French media reports, they barely spoke and Thomas said he did not feel well.

Anne, 16, was the only girl of the four and modeled for a mail-order catalog. She was also the most studious of the four children and attended a Catholic school called La Perverie.

Thirteen-year-old Benoit attended the same school as Anne. Like her older brother Thomas, she was obsessed with music and played the drums.

Xavier, of aristocratic descent and a count after his father's death, aspired to become a businessman, but with limited success. When his father passed away, Xavier learned that there was no money left in the family, but he also apparently inherited the same type of rifle used by the family. In the weeks leading up to the murder, Xavier reportedly learned how to use the gun and purchased cement and quicklime, which were later found on the body. He wrote to family and friends that he and his family were in witness protection with the U.S. Drug Enforcement Administration.

This begs the big question. There are two leading theories (open in new tab) about Xavier's death. Either he committed suicide after traveling to the south of France to revisit his childhood home (he was seen on surveillance video during that trip), or he disappeared and fled to another country. An extensive search was conducted, but no bodies were found. According to an old blog (opens in new tab), members of his family reportedly still do not believe he killed his own family.

Someone claiming to be Xavier sent a note to journalists in 2015 (opens in new tab), and since then there have been numerous sightings of him, but police have been unable to confirm whether these sightings are genuine.

Anyone with information on the Dupont de Ligones family can visit unsolved.com.