Tarkovsky's unpublished screenplay treatment, essentially a short story in present tense, consisting of 6 handwritten pages, called 'Konsentrat' (meaning "the concentrate" or "the extract"), was based on his year-long experiences working as an assistant with a state-guarded secret scientific research expedition to the Siberian taiga at the river Kureikye near Turukhansk in the Krasnoyarsk Province in 1953, for the Academy of Science Institute for Non-Ferrous Metals and Gold, to prospect for natural diamonds for industrial use. His short story is about the leader of a geological expedition, who waits for the boat that brings back the concentrates collected by the expedition, which is surrounded by great mystery, and whose purpose is a state secret. It was written in a single sitting during Tarkovsky's VGIK film school entrance examination taken immediately after his return from the trip in 1954. He received the highest grade for it: a "5" (equivalent to an A), and was admitted to the following semester.
The writers of this documentary and adaptation, Marina and Aleksandr, are respectively the sister of Tarkovsky and her husband who was a classmate of Tarkovsky at film school and who collaborated with him in his first two student short films.