The film is often compared to Andrei Tarkovsky's Stalker, also adapted from a Strugatsky book.

The story has been adjusted slightly to contextualize it in the "near future," with the main character Victor Banev recast as a UN envoy to the town of Tashlinsk, where a mysterious group has taken the town's children to an isolated boarding school.

The major departure from the novel's plot is in the ending, in which the "Aquatters" ("Slimeys" from the novel) are all killed by the humans.

The children are heroically rescued by Banev, but they are unable to reassimilate into society and are institutionalized.

[3] A small role created for the film was a UN negotiator named Gennady Komov, a reference to a popular character from the Strugatskys' other books.