Police work hard to investigate crimes. They follow the evidence and talk to witnesses. But sometimes, that's just not enough. When they need to get close to the criminals they pursue, they call on undercover officers. These special experts learn how to “become” a criminal to infiltrate and gather information. It's an intense job that could end in death at any second. Inside, read how officers train for this unique part of law enforcement, the dangers they face, and how their work has been so successful. Adventure, courage, talent . . . and service–they can all be found in the stories of brave men and women who go . . . ON A MISSION.