It's one of America's most mythic UFO incidents--a 200-yard swath of debris that landed near Roswell, New Mexico. Some believe it was an alien craft, others that it was a secret government experiment. The deeper researchers dig, the more perplexing the story gets. It's a mystery that's endured for nearly 80 years. So what really crashed in Roswell in 1947?

On February 14th, 1929, one of the most shocking murders in mob history goes down in Chicago--and becomes known as the Valentine's Day Massacre. The 20s and 30s are full of gangland murders, but the Valentine's Day Massacre is considered the most brutal -- and the toughest to solve. So who carried out the Valentine's Day Massacre? And why?