Solution—Fordney Sees the Light
When Otto Freund said he mistook the beam of the antiaircraft searchlight and headed for its light, the Professor knew he was lying, because an infrared beam of light is invisible to the human eye! One could stare into an infrared searchlight which is throwing its beam miles into the sky, and see only blackness.
This type of searchlight records any object on which it falls on special photographic plates, thus enabling anti-aircraft guns to be trained on planes the infrared beam picks out.
* * * *
I NEVER SAW AN EYE SO BRIGHT.
—Mrs. Welby