In the mid 1800s New York was a dangerous, chaotic city teaming with newly arrived immigrants. Ruthless crooks and brutal criminal gangs ruled the lawless streets. Host Kelly Choi maps the emergence of the police force that took on these cutthroat thieves and mobsters. Along the way, she highlights the work of some of New York's greatest detectives. She begins with the famous cases of Chief Inspector Thomas Byrnes -- a man who invented America's modern detective bureau.