Two thousand people died during the attack on Pearl Harbor. Had we heeded the clues, could the United States have prevented the bombing?

Grigori Rasputin, a close personal advisor to the Tsar of Russia, refused to die. It took multiple attempts to kill this mystical man.

The “Missingest Man” was Judge Crater, whose 1930 disappearance led to the lengthiest unsolved missing person case in New York City.

The Antikythera Mechanism, a 2,000-year-old astronomical calculator, is probably the most complicated piece of ancient machinery discovered.

Some murder cases are thought to be the work of serial killers. Here are some famous unsolved serial murders in the United States.

Through handwriting analysis, the FBI concluded that all the Anthrax letters were written by the same person. The FBI believes Bruce Ivins was the culprit.

The Amber Room was a coveted treasure from the 18th century, but its fate has been a mystery since WWII. This is the history of the priceless chamber.

Raoul Wallenberg bravely went to Hungary to defy the Nazis and their allies to save Jews. Unfortunately disappeared some months before the war ended.