On 11 September 2001, suicide attackers hijacked two passenger planes flying over the eastern United States and crashed them into the Twin Towers of the World Trade Center in New York, causing both buildings to collapse. The attack killed 2,753 people. As smoke billowed from the burning towers, firefighters, police officers and paramedics from across New York City raced to the scene, climbing stairwells packed with fleeing civilians in an effort to reach those trapped. When the towers fell, hundreds of first responders were still inside, and in the years since, even more have died from illnesses linked to their time working in the toxic dust of Ground Zero. Twenty-five years on, Kirsty Wark travels to New York to bring together the first responders and survivors who lived through that morning. New York Fire Department Battalion Chief Joseph Pfeifer was the first commander on the scene, and later became planning chief for the rescue and recovery effort at Ground Zero. Office worker Richard Eichen, who escaped from the 90th floor of the North Tower. Jill Pila, whose husband Jim Gartenberg worked on the 86th floor. Former NYPD officer Judy Castro, who rushed to the North Tower to help evacuate the building. St John's Hospital paramedic Jimmy Dobson, who spent the day bringing the injured to safety from the streets surrounding Ground Zero. Rear Admiral Michael Day, who coordinated the evacuation of an estimated 500,000 people off the island of Manhattan later that day. And the novelist A.M. Homes, a longtime resident of New York, who witnessed the events of the day unfold from her apartment in Lower Manhattan.