"A mysterious object found in a Davenport home turned out not to be a bomb, but a device that was supposed to scare off aliens believed to be living under the ground... Jessica Harper of Bettendorf said she moved out ... on Sept. 29 and left behind a box containing the device, which the Quad-City Bomb Squad investigated Sunday. She said a friend of her mother who lives in Colorado sent the box about a year ago, but they never bothered to open it or throw it away.
... the device was supposed to set off vibrations that would keep aliens away. Harper added that she did not know what the device looked like since they never opened the box." - qctimes
Obviously, the device worked fine. It kept all underground aliens away from that home... until now. They don't really have to be aliens. If a past race of humans moved under the ground, for example, to avoid wars on the surface, and continued to flourish and progress technically for thousands of years ... might they be the cause of many currently inexplicable phenomena?