Sophie had arrived in Ireland alone on 20 December, planning to return to Paris for Christmas. A neighbour found her body at 10 AM on the 23rd, in the laneway beside her house. She was wearing nightwear and boots, as though she had been roused from bed and had run outside. Her longjohns were caught on a barbed-wire fence. Bloodstains marked a gate, a piece of slate, and a concrete block. The State pathologist, Dr. John Harbison, did not arrive for 28 hours. When he did, he found fractures of the skull and multiple blunt-force head injuries so severe that Sophie's own neighbour could not formally identify her face. Her body had been left outdoors for the entire intervening period. The investigation was compromised from the start.

Ian Bailey, a British-born freelance journalist and sometime fish factory worker who lived with his partner in nearby Goleen, quickly drew the attention of investigators. He was known to local Gardai from prior incidents of domestic violence that had hospitalized his partner. In the days after the murder, Bailey had unexplained scratches on his forearms and an injury to his forehead, which he attributed to cutting down a Christmas tree. Investigators could not reproduce such injuries by cutting trees, and witnesses who had been with him the evening before the murder recalled no scratches. His alibi shifted: initially he and his partner both said he had been in bed all night. She later retracted that account, saying he had left the bed around 11 PM and returned at 9 AM with a fresh wound. Several witnesses reported that Bailey told them he was covering the murder of a French woman before that information had been released. At the 2019 Paris trial, witnesses testified that Bailey had confessed to them on separate occasions -- "I did it, I did it -- I went too far" -- though Bailey disputed every claim.

Bailey was arrested twice by the Garda Siochana but never charged in Ireland. The Director of Public Prosecutions found insufficient evidence to proceed to trial. Bailey lost a libel case against six newspapers in 2003 and a wrongful arrest case against the Gardai in 2015. Meanwhile, Sophie's family, through the Association for the Truth on the Murder of Sophie Toscan du Plantier, pursued the case in France, where the law claims jurisdiction over the murder of any French citizen anywhere in the world. A European Arrest Warrant was issued in 2010, but the Irish Supreme Court blocked extradition in 2012, ruling that the offence occurred outside French territory and that reciprocity was absent. In 2019, a French Cour d'Assises convicted Bailey in absentia and sentenced him to 25 years. Ireland's High Court ruled in October 2020 that he could not be extradited. The Irish State chose not to appeal.

Ian Bailey died of a suspected cardiac arrest outside his residence in Bantry on 21 January 2024, aged sixty-six. After his death, Gardai searched his flat under warrant, taking a laptop, memory sticks, notebooks, and items for DNA profiling. The Garda Serious Crime Review Team had already announced a full review of the case in 2022. Whether that review will produce answers is uncertain. What is certain is that Sophie Toscan du Plantier's murder transformed this quiet stretch of West Cork into one of the most intensely examined crime scenes in the world, the subject of Netflix documentaries, podcasts, Jim Sheridan films, and at least half a dozen books. The cottage near Toormore still stands at the end of its lane, in countryside that remains beautiful and remote, and the case -- despite a conviction in one country and decades of investigation in another -- remains, in Ireland, officially unsolved.