The C38 Mysteron detector is a portable Roentgen radiation ("x-ray") camera used to detect Mysteron likenesses.
The detector, when shown, has been used primarily on Earthmen--and Mysteron likenesses of Earthmen. Whether it can also determine if objects have been taken over by the Mysterons is generally taken for granted, even in fanon. This last has not been gauged.
How the detector's base principle was discovered
The principle behind the Mysteron detector was discovered accidentally, when the Mysterons' likeness of Dr. Theodore Magnus attempted, unsuccessfully as it proved, to assassinate General J. F. Tiempo, the commander of the Western Legion World Defence, in "Operation Time." The original Theodore Magnus, a highly prominent and indeed world-renowned neurosurgeon, was one of the few physicians who still relied on x-rays in the late 2060s.
(The Mysterons' intended weapon against General Tiempo was a "cerebral pulsator" of the original Dr. Magnus' own design, which apparently worked by generating microwaves with two electrodes that were attached to the patient's scalp. These would then bombard any diseased brain tissue at which the electrodes were aimed, burning and thereby necrotising that tissue out of the brain. Thus it was essentially a non-optical "maser" such as were presumably commonly used in surgery in the 2060s. If the microwave intensity was adjusted too high, however, as the Magnus likeness did in attempting to assassinate Tiempo but instead killing Captain Scarlet, then the microwaves would instead necrotise the patient's entire brain and reduce it to what amounted to cooked meat.)
The Magnus likeness impatiently wanted to get started on carrying out the Mysteron threat and carelessly brought his hand in front of the x-ray camera when he was shooting the last picture of Tiempo before the actual surgery was to commence. After the x-ray film was developed, the image of the Magnus likeness' hand and forearm gradually became visible in monochrome upon the film, clearly blocking the area that was being x-rayed at the time. The radiographer of the original Magnus noted this at first with annoyance, then with growing horror. For it indicated that a Mysteron likeness would be impervious to Roentgen radiation.
How the detector works
The detector works by projecting Roentgen radiation at a suspected Mysteron likeness whilst its user shoots a photograph of the same. After not longer than five seconds, the image has developed and is printed. If the subject is a normal Earthman, the printed image will show a skeletal view, therefore giving a negative result; if a Mysteron likeness, it will show a photographic view in monochrome, therefore giving a positive result.
Since Captain Scarlet was once under Mysteron control, his body has become impervious to Roentgen radiation, and hence use of the detector on him will produce a positive result, making him an ideal "control" subject for its use. Indeed, this has enabled fanon writers to speculate that Mysteron detectors are calibrated by using them on him whilst he is standing side by side with another Spectrum senior officer.
The detector can also work in any atmosphere, even in complete darkness. Owing to the Law of Inverse Squares, however, its maximum practical range is approximately fifty yards, or roughly fifty metres. The Mysteron rifle has a similar such effective range.
It proved its effectiveness when it revealed that former Spectrum officer Captain Indigo had become a Mysteron agent.
New Captain Scarlet