It's 8:48 on Tuesday morning, two weeks to the minute that the first hijacked jet crashed into the World Trade Center. At Ground Zero, where more than 6,000 people are still missing, the solemn search for any sign of life goes on. But even this vital work must stop to remember the thousands who are lost somewhere in these mountains of debris. Assistant Fire Chief Frank Fellini has been at Ground Zero since the first hours of the attack. "Almost everyone knew someone. I've met five or six firefighter fathers looking for sons and sons looking for their fathers." 48 Hours was granted unprecedented access to both Ground Zero and the command center of New York's Office of Emergency Management. An army of 20,000 city, state and federal workers as well as volunteers are on the front lines, carefully sifting through debris.