The play starts from the narrator named Tom Wingfield introducing himself and telling the audience that the events of the play are his memories about his life ten years ago - just made brighter for them to see. The time of the play is 1930s and the place is small town of St. Louis.
Tom is a young man, he writes poetry and hopes to become a famous poet once. But now he is also the only breadwinner in his family - his father left the family years ago, sent a single postcard and never contacted either his wife Amanda Wingfield or his two children - Tom and Laura. Despite his dreamy and romantic nature Tom has to do the mundane job in a shoe warehouse.
All the family members try to forget about their miserable life. Tom himself uses alcohol, adventure books and movies to distract himself after the work. Laura, the equally dreamy young girl, who survived a serious illness in childhood that left her limping, is painfully shy. She never goes out with anyone, spending her time with her collection of glass animals that Tom jokingly calls “the glass menagerie”. These animals are the most precious of her possessions.
Amanda found more practical way to escape. She often lectures her children for being too naive and romantic, not accepting the real life, but the woman herself is immersed in the past just as much as they are in their dreams. She tells Tom her never ending stories about her youth, her gorgeous life in the South and countless suitors that dreamt of her. Partly these stories are real but mostly they are also fantasies that help Amanda to dissociate from her present ruined life. The only way to improve her own life she sees in her children. She demands that Tom works more thoroughly, blames him of everything and tries to change him to suit her goals. But soon she understands that this tactic only provokes more conflicts between her and Tom. The only time her son stopped arguing about his job was when Tom angrily waved his hand and accidentally broke some of Laura’s glass animals. Seeing that nothing can be done here right now, Amanda switches her attention to Laura who is much easier to control.
At first Amanda makes Laura enroll to a business school. She wants her daughter to become a typist and earn at least as much as Tom does. But what makes Laura so controllable - her extremely low self-esteem - also effectively bans her from study. The poor girl is stressed so much that her hands are constantly trembling and she can’t hit the buttons of the typewriter. After two weeks of suffering Laura ceases to study to Amanda’s great disappointment.
One plan is a failure, but Amada has a backup one. Despite unable to work among other people, Laura can still be married to the wealthy man. But Laura doesn’t even have friends to choose from! Amanda tries more cunning strategy. From the one hand she tries to influence her son indirectly, criticizing the literature Tom reads - especially Lawrence’s novels - as “dirty” and his way to spend his evenings in the cinema. She offers him to invite some of his friends home instead to have a good time and also give his beloved sister a chance to find a decent man.
Tom hesitates for a long time but finally agrees. He invites his colleague, Jim O’Connor to the dinner. Jim is the only person in the whole warehouse who understands Tom and really is his friend. Amanda conducts a real interrogation and is satisfied to hear that Jim is very determined and is going to be promoted soon. She starts preparing apathetic Laura insisting on her wearing her best dress and cleaning up nicely in general. But when Amanda tells the name of their guest, Laura is shocked. It is the boy she had a hopeless crush for all her school years. Jim was always the most popular, attractive and smart. He was a captain of a basketball team, led the debate club, sang in school plays - the shy and average limping girl had absolutely no chances to draw his attention. Laura understands that the dinner with Jim, whom she still loves, will be a torture for her. She doesn’t dare to utterly disobey her mother (who has already prepared a fancy dinner and cleaned the house). Laura opens the door to Jim, greets him and disappears at once, leaving him with Tom. She even pretends to be sick to avoid having dinner with Jim - the poor girl doesn’t need to act too much, she is really almost fainting from stress.
Tom now has time to talk to Jim in private. He confesses that he took money that he saved for paying the electric bill to leave his family and go seek adventures somewhere. It seems now Jim understands why his friend is so desperate to run away from home. Especially when Amanda greets him wearing an especially elaborate dress from her past and starts to talk to him overly sweetly and pretend to be incredibly nice and glad to see him.
After the dinner the lights go out - the electricity is switched off due to unpaid bill. Amanda uses it to her benefit, asking Jim to calm down the possibly frightened Laura while she and Tom are doing the dishes. Jim goes upstairs and sees Laura. The young people are both equally shocked: Jim didn’t know that his schoolmate is the sister of his friend. At first Laura is extremely reserved, not knowing what to do and how to speak, but Jim warmly and cheerfully talks her out of this state. He reminds her the school nickname he gave her - “Blue Roses”. He warped the name of her illness - pleurosis - and turned it into affectionate nickname that shall always remind Laura that she is unique and unusual, just as blue rose is.
Gradually, Laura warms up and starts talking back to Jim. She is relieved of her stress and now talks to him just like Tom does - like with an old friend. The girl even shows him her glass menagerie. Jim notices a unicorn among the other creatures and picks it, saying that it must feel incredibly uncomfortable amongst the average earthly creatures but it’s not because something is wrong with it. The unicorn is beautiful, just as Laura is, it simply haven’t met its own kind yet. Jim convinces her that no one in all the school noticed she wore orthopedic shoes and was limping. He tells Laura that people aren’t evil and no one wants to harm her, its her imagination and self-loathing that make the world seem such a bad place. Jim even invites her to dance when he hears a waltz sounding from the restaurant nearby. Laura is embarrassed, she is afraid to step on his foot - but Jim jokingly replies that he is not a member of her glass menagerie so he won’t break because of it. They start to dance, but Laura is a bit clumsy indeed and the dancing pair accidentally break the glass unicorn. Mostly the figurine is fine but its horn is gone and now it’s just an average horse.
If it was anyone except Jim Laura would be heartbroken, but now she forgives him easily. It seems she now has something more real and dear to her than her glass figurines. Especially when Jim leans to her and gently kisses the girl. Laura is almost unconscious, feeling happier than ever before - but Jim immediately comes to his senses. Seeing the reaction of the girl and understanding she took it way too serious, he is frightened. Jim tries to gently calm her down explaining that he just wanted her to feel special and become more confident and he went too far in his attempt, caught by the moment. He actually has a real girlfriend and they are engaged, but he is sure that Laura will find her own happiness very soon.
Laura understands. For her, always thinking of herself as of unworthy, all that happened is too good to be true. She solemnly forgives Jim and thanks him for the wonderful evening. She presents him a broken unicorn in memory of their dance and asks to think of her occasionally.
Amanda enters Laura’s room. She is upbeat and happy, playfully joking with both. Her appearance is a dissonance with a quiet scene in the room. However, Jim politely but coldly replies that he has to hurry to the train station and meet his fiancée there. He thanks for the dinner and quickly leaves. Amanda is sweet until the door is closed behind Jim but then, furious, she storms to Tom (who didn’t know Jim was engaged) shouting at him for bringing home the wrong man, wasting her time and food for dinner and disappointing his sister. Laura, who also kept her composure before Jim left, now bursts into tears. Amanda rushes to her, dramatically calming her down and trying to comfort her.
The memories end. The narrator concludes that in a few weeks he got fired from his job and finally left his home starting his journey. The only thing that haunts him is Laura, crying because of him. Tom has never seen him again, but still feels guilty because of that evening. He is sorry that he left his sister, who he was so devoted to, behind and will always remember how sweet, sad and beautiful she was that night, blowing a candle before going to bed.