Japan has a mystery on its hands. A worker has discovered a drone on top of Prime Minister Shinzo Abe's office that was not only carrying a water bottle, but was marked with a radioactive sign and carried a "miniscule" amount of radiation, according to officials. While the quantity wasn't enough to harm anyone, the landing raised more than a few alarms, as you can see by the giant tarp and swarm of police in the photo here. Who was behind it? And how did they get on to the roof undetected?