Based on a novel of the same name, a work of Soviet-era writers - Arkady and Boris Strugatsky (otherwise known to some extent among sci-fi enthusiasts for their more known novel, Roadside Picnic, or the entire Stalker franchise that stemmed from it).
The movie starts with a middle-aged writer Viktor Banev (writers seem to inhabit Strugatsky brother's works frequently, adding flare to philosophical discussions which are often lead) who later becomes known for seeking after his daughter, which was sent off to a private school for prodigies. Her father, seemingly desperate, but a very cunning and determined man searches for a way into the quarantined city where the school is located, employing the help of a midget professor associated with the anomalous quarantined zone in which the entire ordeal is taking place. The address of the professor appears to him in a dream as he claims in the movie, an explanation which the professor found humorous – and probably at that moment decided not to make Swiss cheese out of the lone writer with the shotgun he kept in his hands, all due to his cautious nature, and the peculiar meeting the two of them had.
Banev is next transported into the scene, getting past the military blockade, eager to meet his daughter. He soon learns that visitors from a foreign planet or dimension manifested themselves to give guidance to the prodigies, being at a loss for contradictory human thinking and behavior. How can philanthropy exist when the philanthropist himself is hated by those he tries to help, and why does the philanthropist even try? Why does he not despise those he helps, as they do him? The aliens have little time to learn of all the human peculiarities, so their benevolent intentions are thought of as a threat, their acts of self preservation a direct assault on the human race.
The heavy suspense and the direness of the situation unfolding is heavily created by the environment - the heavy muddy floods and the constant outpour of rain caused by an anomaly - a supernatural alien formation hovering ominously above the city. Gloom hovers above those trapped inside the city - themselves becoming scaly creatures the scientists and military named Aquatters - but only if their will drags them toward the power and knowledge the peculiar area is capable of granting.
The story culminates with the military deciding to carpet bomb the entire place, as they would do in real life should we ever encounter aliens anywhere, the writer and his daughter crawling down in a bomb shelter and waiting it out, as they were unable to evacuate in time - him singing a limerick while the poisonous gas seeps outside.
The final scene deals with his daughter being institutionalized in a prison-like facility, the desperate father itching to bring back his changed child, incapable of reintegrating back to society - the ugly swan.