The documentary entitled 'Janez Puhar's Lost Formula' introduces the Slovenian inventor of glass-plate photography from the point of view of a foreign observer, that of Scotsman Robin Crichton, who wonders how and why we honour him, since he is virtually unknown in the Western world. Robin decides to single-handedly look into these Slovenian beliefs. Puhar claims that for the light-sensitive matter he used mercury, sulfur, iodine and possibly varnish, which he applied in the end to protect the emulsion. But his real formula has never been brought to light anywhere. Indeed, the whole world knows that no one has used Puhar's ingredients to make photographs, because the said three elements are not sensitive to light - neither separately nor together as a compound. Robin therefore arrives at the key question: are the four Puhar originals, which currently exist around the world, real or are they just a mistake made by Slovenian historians and museum specialists?