In France, it’s known as the "House of Terror": an elegant home in the city of Nantes where a woman and her four children were found buried in April 2011.
It’s a terrible crime that has obsessed the French for nine years. But now that it’s been featured in Netflix’s Unsolved Mysteries, there’s hope that the person responsible for the killings could finally be found and brought to justice.
The house belonged to Count Xavier Dupont de Ligonnes, a businessman who lived there with his wife Agnes, a teaching assistant, and their children Arthur, Thomas, Anne and Benoit. The family seemed like they had it all.
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They were good-looking (Anne was a part-time model) and clever. But Xavier was hiding something – or perhaps several things. Financially, he was in major trouble. It’s also alleged that he had a mistress in Paris.
French media have published an email he supposedly sent to his mistress, where he said he was "ruined, at rock bottom" and lying awake with "morbid ideas".
"Most of the time I am not in a dream but in a nightmare and I can't escape except, of course, by doing something radical and final," the email read.
Xavier’s father died in January 2011, with barely any money to his name. Among the possessions that Xavier inherited from him was a rifle. Soon afterwards, he got a gun licence and bought a silencer.
In early April, Xavier told his children’s school that the family was moving to Australia. The school that Agnes worked for was told the same thing.
Thomas, who was living at a university hall of residence, received a call from his father telling him to come home because his mother had been in a serious bicycle accident. Neighbours heard howling from the family’s Labradors, Jules and Leon, which lasted two nights and then stopped.
In mid-April, the families and friends of Xavier and Agnes received strange letters, purportedly from the couple.
The letters claimed that Xavier was a spy for the US drug squad and he’d been transferred to the US to infiltrate an international drug ring.
"Keep it secret!" the letters urged.