In the hospital, Belt continues to wrestle with the presence, telling Mulder he wasn't responsible but also couldn't stop it, as "it came to me, it lives in me". Eventually, in a last struggle with the re-possessing entity, he leaps from the window to his deathexperiencing a lengthy flashback to his last space mission as he falls.
The passage describes Belt's struggle against an entity that has taken control of him.  He is overwhelmed by this presence and attempts to fight it, leading to a final act of defiance where he jumps from a window. The flashback serves as a symbolic representation of his past experiences and how they relate to the present situation.