Conspiracy theory over UFOs and missing scientists spreads from web to White House

Are the disappearances or deaths of at least 11 US scientists, each allegedly connected in some way to space, defense and nuclear research, really linked in a nefarious plot: one that involves the Chinese or other state enemies, or possibly links back to UFOs?

A conspiracy theory positing exactly that has roared through sections of the US population in recent weeks, spreading rapidly from the internet into rightwing media and hence into the mainstream press and prompting an inquiry from Congress and questions from Donald Trump.

Could such an outlandish theory have even an inkling of truth? Or are lawmakers, the FBI,