Unsolved Mysteries Season 1, Episode 3 comes bearing the thriller-esque title "House of Terror." It's based on the unsolved 2011 murder of Agnès Dupont de Ligonnès and her four children, Arthur, Thomas, Anne, and Benoît. All five of their bodies were found buried under the porch of the family home in France. The police even had a suspect: The father, an aristocrat named Xavier DuPont De Ligonnès. Their only problem was, Xavier had disappeared and has never been found. These theories about Xavier Dupont De Ligonnès and where he might have gone explain why cases like this are so hard to solve.
Warning: Spoilers for Unsolved Mysteries Season 1 follow. The case is a horror show. Not only were Agnes and her four young children murdered, bagged, and buried under the house with religious icons next to them, but also, whoever did this killed both family dogs as well, and buried them too. According to the episode, all four children were given sleeping pills and then shot.
The lack of any evidence of anyone else breaking into the house and the amount of care taken in these killings and burials point to the murderer being Xavier — especially when it was revealed that Xavier, who was born the son of a count, had squandered the family fortune. By the time of the murders, he was deep in debt, and his father's death left him in charge of a legacy he could not save. However, his sister insists her brother is innocent.
That being said, Xavier's disappearance has meant this case has never been closed. Here are a few theories about what happened.