In The Thing in the Window, Martin Ames, a struggling actor, becomes increasingly obsessed with a figure he believes to be a dead body in an apartment window across the street. The story begins with Martin noticing the figure, slumped in a chair behind blue draperies, and he is convinced that it is a corpse. Despite his attempts to share his concerns with others, including his housekeeper Mary and the apartment superintendent, no one else can see the figure, leading Martin to question his own sanity. The tension escalates as he grapples with the possibility that he is witnessing a crime or succumbing to a delusion.