First broadcast on ATV London 12 April 1959.
Aircraft testing a new fuel diffuser keep crashing. The Invisible Man steps in to help discover the cause, which is sabotage, naturally.
OK episode that suffers from a lack of definition. Why the fuel diffuser is so important is never explained, nor why the bad guys want to prevent it being developed. Probably the best thing about this one is to see long-time extra Victor Harrington actually get a couple of lines of dialogue!