One day, Gregor Samsa, a traveling salesman, wakes up to find himself transformed into an ungeheures Ungeziefer, literally "monstrous vermin", often interpreted as a giant bug or insect. He believes it is a dream and reflects on how dreary life as a traveling salesman is. As he looks at the wall clock, he realizes he has overslept and missed his train for work. He ponders the consequences of this delay.
Gregor becomes annoyed at how his boss never accepts excuses or explanations from any of his employees no matter how hard-working they are, displaying an apparent lack of trusting abilities.
Gregor's mother knocks on the door, and he answers her. She is concerned for Gregor because he is late for work, which is unorthodox for him. Gregor answers his mother and realizes that his voice has changed, but his answer is short, so his mother does not notice the voice change. His sister, Grete, to whom he was very close, then whispers through the door and begs him to open it. He tries to get out of bed but is incapable of moving his body. While trying to move, he finds that his office manager, the chief clerk, has shown up to check on him. He finally rocks his body to the floor and calls out that he will open the door shortly.
Gregor is the main character of the story. He works as a traveling salesman in order to provide money for his sister and parents. He wakes up one morning finding himself transformed into an insect. After the metamorphosis, Gregor becomes unable to work and is confined to his room for the remainder of the story. This prompts his family to begin working once again.
Grete is Gregor's younger sister, who becomes his caretaker after his metamorphosis. Initially Grete and Gregor have a close relationship, but this quickly fades. While Grete initially volunteers to feed him and clean his room, she grows increasingly impatient with the burden and begins to leave his room in disarray out of spite. She plays the violin and dreams of going to the conservatory, a dream Gregor had intended to make happen; Gregor had planned on making the announcement on Christmas Day. To help provide an income for the family after Gregor's transformation, she starts working as a salesgirl.