Beloved Hero of the Soviet Union, Commanding Officer Konstantin Sergeyevich Veshnyakov is one of two cosmonauts aboard the Orbit-4 during an orbital research mission in the year 1983. When something horrific interferes and the spacecraft crashes upon re-entry, he is the only survivor — seemingly. In truth, Konstantin has unwillingly brought something back with him to Earth. Something that chose his body to make its "spacesuit" while it tries to survive in this new, foreign world.
While the public is told that the two cosmonauts are safely recovering in a rehabilitation complex, truthfully Konstantin is brought to an isolated military research facility, from which he plans to escape in order to reunite with his mother and retrieve his son from an orphanage. However, there are nefarious plans afoot to try and utilise the cosmonaut and his alien sputnik as a weapon of war.
Konstantin himself embodies the concept of the New Soviet Man. He is the posterchild of The Ideal: athletic, handsome, healthy, disciplined, intelligent, a proud Communist, a Commander and a cosmonaut — and a lingering representation of this concept that, by his time, was beginning to be dissolved. "Loved by women and children", he is affable, well-spoken, and appropriately charming: playfully flirtatious or reliably serious when he needs to be. His reputation is his livelihood and identity alike, and he covers up the less desirable parts of himself and his past well — until, of course, everything comes (quite literally) crashing down. Now the once-proud cosmonaut is a fallen hero, one who feels his horrific fate as the alien's chosen host is a justifiable punishment, and who will stop at nothing to help the one who needs him the most — his son, Aleksei "Lyosha" Konstantinovich Romanov.
( cw: mention of suicide )
In the process of escaping from the facility, Konstantin manages to forcefully expel the creature from his body by injecting himself with a concoction that mimics the symptoms of a disease. However, the longer they stay apart, the sicker he becomes, solidifying the concept that they are truly "bonded" and can not survive without one another. The alien, who has been severely wounded by the military, returns to Konstantin's body, where both of them can slowly start the process of healing. However, when more of the military's trucks begin approaching, Konstantin realises he can neither escape being recaptured nor ever be freed from the creature, and so he shoots and kills himself in the abdomen — also killing the alien.
From there, he wakes up in a snowy landscape that isn't the world he just came from — somehow still alive, wounded, but healed to the point the wounds aren't fatal.