Penn Zero: Part-Time Hero - All Episodes

20/20 continues to combine hard-hitting investigative reports, newsmaker interviews and compelling human interest and feature stories.

An emotional thrill ride through the day-to-day chaos of the city's newest state-of-the-art trauma center and into the lives of the courageous doctors, nurses and staff who hold it all together. This is one of those days.

The Rookie is inspired by a true story. John Nolan is the oldest rookie in the LAPD. At an age where most are at the peak of their career, Nolan cast aside his comfortable, small town life and moved to L.A. to pursue his dream of being a cop. Now, surrounded by rookies twenty years his junior, Nolan must navigate the dangerous, humorous and unpredictable world of a "young" cop, determined to make his second shot at life count.

District 21 of the Chicago Police Department is made up of two distinctly different groups. There are the uniformed cops who patrol the beat and go head to head with the city's street crimes. And there's the Intelligence Unit, the team that combats the city's major offenses - organized crime, drug trafficking, high profile murders and beyond. These are their stories.

No job is more stressful, dangerous or exhilarating than those of the Firefighters, Rescue Squad and Paramedics of Chicago Firehouse 51. These are the courageous men and women who forge headfirst into danger when everyone else is running the other way and whose actions make the difference between life and death. These are their stories.