As a hijacked plane hits the North Tower, we follow the first firefighters on the scene and their race against time to rescue trapped civilians.

We follow extraordinary stories of escape in the South Tower and the paramedics on the ground facing an onslaught of badly injured people.

This segment covers the time span from 9:40 - 10:50am, which is roughly the period from Pentagon attack to Shanksville crash to before the second tower's collapse.

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.