Tennessee Williams' most famous plays, "The Glass Menagerie," "Cat on a Hot Tin Roof," and "A Streetcar Named Desire," as well as some of his other plays tend to not be upbeat, let alone comedic. They are, in fact, just the opposite. Whether portrarying the lower strata of socieity, as in "Streetcar," or the upper classes, as in "Cat," the themes tend to be serious discussions of dysfunctionality within families. The dynamics that take place during the course of a Tennessee Williams play often represent the darker, more somber sides of American life. That "The Glass Menagerie" takes place in dark settings, mostly in Amanda Wingfield's apartment, and features a family in some kind of crisis, is consistent with Williams' approach to his subjects.
Amanda's daughter, Laura, is sweet, but sickly, shy, and partially disabled from illness, and is essentially a shut-in, afraid to venture beyond the threshhold of the apartment door. The lighting in the apartment is subdued, in keeping with the themes of despair and hopelessness that characterize some of Williams' characters. The darkness of the atmosphere is compounded when the electricity fails, and an already gloomy interior is rendered much darker -- all the better given the news that the man Amanda's son Tom has brought home to meet Laura confides that he is engaged to be married.
The play ends with Tom leaving, apparently for good, Amanda angry with Tom, and Laura set to withdraw back into herself. The final scene shows Laura blowing out the candle in her bedroom, symbolic perhaps of the darkness to which Amanda and Laura will now return.