Fentanyl is posing a serious danger across the U.S. The drug, which is 50 times more potent than heroin, kills an estimated 150 people a day.But is the danger of the drug truly recognized and understood? The truth is that many people dying from fentanyl exposure didn't even know they were taking the drug. RELATED STORY | How a 5-year-old ingested fentanyl in her kindergarten classroomIn "To Save a Life: A National Fentanyl Alarm," people share their stories to understand how we got here and how we solve the problem. Watch the full special in the player above.