A day of terror and the struggle to survive continues as the Pentagon is hit, Flight 93 is hijacked and the South Tower collapses.

Survivors become separated when they are enveloped by a toxic dust cloud. We follow their quest to be reunited with their loved ones.

A group of firefighters were inside the North Tower when it collapsed, but miraculously survived. It's a race against time to find and rescue them.

At Ground Zero, two ex-marines and an ex-paramedic join forces to search for survivors and pull off one of the most miraculous rescues of the day.