A person is suffering from Cotard Delusion or Walking Corpse Syndrome. He has lot of false delusions, the most prominent one is that he thinks he is dead or doesn't exist and someone is trailing him under his bed.
The story revolves around an individual living with a psychotic disorder, consistently suffering with terrifying thoughts and actions quarantined in his room, under medication. His Cotard delusion or Walking corpse syndrome is making him investigate an existence of the truth of an uninvited guest under his bed, haunting his nights.—Anshul Pal