The NIH team teams up with the officers of the 55th Precinct in New York City to try to figure out what is the source of an outbreak of Marburg, a deadly disease with no known cure. They also try to locate patient zero, a murder suspect on the run, who is helping to spread the disease throughout New York City.

This was a special non-fiction episode which told, in their own words, the real stories of the police officers, firefighters, paramedics, emergency services personnel, and their families in the aftermath of 9/11/01. The regular starring cast members did brief introductions to each of this documentary's segments, which featured the real police officers, firefighters, paramedics, and emergency services personnel who work as part-time technical advisors and cast members in the production of every regular ""Third Watch"" episode.