On 19 November 2005, US Marines killed 24 civilians in Haditha, Iraq, many of them women and children. The incident led to the longest US war crimes investigation of the Iraq war. But in the end, no one went to prison. A four-year investigation by BBC Eye has uncovered footage, legal documents and marine testimonies that have never before been made public. Reporter Lara El Gibaly speaks to the forensic investigator and lawyers involved in the case, who are speaking out about what happened, and why those responsible for the deaths walked free. And she travels to Iraq to take this information to the survivors, Safa and Khalid, who have been searching for answers about the killing of their families for twenty years.