I Spy... — John Russell Fearn

Television experimenter Curtis Drew sets out to combine the X-ray with television to aid surgery. However, he discovers instead 'pure' television-invisible 'Z-rays' which have the potential to receive and record any situation-anywhere. Nothing is private any more. The secrets of the warlords, the immoralities of the masses, the hidden crimes all be lie exposed before the merciless, penetrating power of the invisible Z-ray. The invention could benefit humanity, yet to Drew it opens up more lucrative possibilities. He becomes a scientific 'Peeping Tom' and blackmailer, but when murder results, Scotland Yard becomes interested...