The Metamorphosis The Office Manager Quotes

[T]he manager burst out with a loud "Oh!" – it sounded like a rush of wind – and now he could see him standing closest to the door, his hand pressed over his open mouth slowly backing away, as if repulsed by an invisible, unrelenting force. (1.25)

While up to this point Gregor's isolation seems to be self-inflicted, the manager's reaction shows how Gregor's isolation is also imposed upon Gregor by the people around him. Before he was turned into a vermin, Gregor chose the lonely life of a traveling salesman, and chose to lock his doors in his own home at night. After the change, it will be the others who lock him up in his room.