Unsolved Mysteries: The 2 Biggest Theories About the Horrific Dupont de Ligonnès Case

A chilling reboot, Netflix's true-crime anthology series Unsolved Mysteries cracks open the tragic case of the Dupont de Ligonnès family in its third episode. Once home to an outwardly wholesome group of people, the Dupont de Ligonnès residence, located in Nantes, France, now has the nickname "the house of horror." There's no sugarcoating the case: on April 21, 2011, investigators discovered the remains of five humans and two dogs buried beneath the terrace.

The bodies belonged to the family matriarch, Agnès, and her four children: Arthur, Thomas, Anne, and Benoît. The two dogs were the family Labradors. The bodies were wrapped in bags, covered in quicklime, and hidden with religious icons. The autopsy found that the children were given sleeping pills — the mother was not, but she did use a sleep apnea machine. Each person was seemingly put to sleep, then shot at least twice in the head with bullets from a .22 rifle.

The primary suspect was the one person not in the gruesome picture: the seemingly devoted father and husband, 50-year-old Xavier. At a cursory glance, it seemed impossible that Dupont de Ligonnès would kill his family in cold blood. In fact, if he did, he was careful not to leave a trace of biological evidence — no blood or fingerprints implicated him. But follow the crumbs of evidence, and murder won't seem at all outside of the realm of possibility.

Dupont de Ligonnès came from an aristocratic French family — his father was, in fact, a count. He made a living as a business owner, creating companies that didn't see all that much success over the years. By the time of his family's death, Dupont de Ligonnès was deep in debt. Months before the family massacre, his father Hubert passed away. While a noble by blood, Hubert died without money. Dupont de Ligonnès inherited one notable item: a .22 long rifle.

Before the family massacre, Dupont de Ligonnès had practiced regularly at a shooting club. He also bought a silencer — in fact, neighbors did not report hearing any sounds the nights the killings took place. Other odd events unfolded: In front of the letter box, someone taped a sign requesting all mail be returned to senders. Dupont de Ligonnès sent bizarre letters to friends and family, explaining that he was a secret agent who had been recruited by America's Drug Enforcement Administration to infiltrate an international drug ring. He noted that he and his family had moved to America, where they took on new identities and were taken into protective custody. The children's schools were informed that the family was moving to Australia.

So what did the timeline of the actual murders look like? Based on the autopsy and evidence, investigators believe that Agnès, Arthur, Anne, and Benoît were killed the night of April 3 (or early April 4), though the exact date has been disputed. Dupont de Ligonnès' son Thomas had still been at university but returned home when he was told his mother had been in a cycling accident. He was likely killed the night of April 5. His death is significant because he would technically be Dupont de Ligonnès' last heir as his eldest biological son — Arthur, Agnès' oldest, was not Xavier's by blood, but he did take him as his son. Shortly after the bodies were found, police discovered his car at a hotel in Roquebrune-sur-Argens.

Following the family massacre, Dupont de Ligonnès left traces of himself throughout southern France, checking into various hotels and restaurants. He withdrew money from his bank card. His car could be identified in speed cam footage, his face in security camera playbacks. Hotel security footage last showed Dupont de Ligonnès carrying a bag and a long object, the latter likely his inherited rifle, on April 15. He was never seen again.

What happened to Xavier Dupont de Ligonnès? The mystery persists, but there are two main theories regarding his whereabouts.