The denouement of Hughes's story is when Mrs. Jones closes the door on Roger, leaving him to navigate his future choices.
The denouement--or declining action following the climax of the plot--of "Thank you, M'am" takes place at the end of the story. Mrs. Jones has given Roger the money he so coveted. She then leads him to the front door, leaving him in the hallway as he stares at her. She tells him to "Behave yourself" as she closes the door on him. Roger could not say anything "else other than 'Thank you, m’am' to Mrs. Luella Bates Washington Jones." The reader is told that he never sees her again.
This scene represents the denouement because it is the final element of the story. The meaning of the title comes into focus while the characterizations of both Roger and Mrs. Jones become fully developed. This moment represents the declining action before the reader experiences resolution. In many ways, Hughes creates an effective denouement because we are like Roger in that there is much more we wish to ask Mrs. Jones' character. However, the declining action of the story shuts the door on us. Therefore, the denouement of the story is Roger standing in the hallway after Mrs. Jones has closed the door on him with the advice: "behave yourself."