Act I of Top Girls takes place in a hip London restaurant where Marlene is gathering five other women to celebrate her promotion to managing director of Top Girls, the employment agency where she works. This scene is surreal, because Marlene's 5 dinner guests are female figures from different historical eras: Isabella Bird; a 19th century writer and traveler, Lady Nijo; a 13th century courtesan and later, Buddhist nun, Dull Gret; the subject of a Brueghel painting who led an army of women into hell to fight the devils, Pope Joan; a 9th century woman who disguised herself as a man and became Pope, and Patient Griselda; the obedient wife from The Clerk's Tale in Chaucer's The Canterbury Tales. These women are bound together by their struggles against patriarchy and oppression - and Marlene relates to each of them differently.
Act 2 is set at the Top Girls employment agency. Marlene is interviewing a woman named Jeanine who wants a new job because there are no prospects for advancement at her current position. Through her questions, Marlene reveals that she looks down on Jeanine for her desire to get married young, have children, and her uncertainty about her professional future. Marlene only offers Jeanine two openings, one at a company that makes knitwear and the other lampshades - neither of which fulfill Jeanine's request for opportunities and travel. Regardless, Marlene tells Jeanine to be confident and present herself well, because her performance reflects on Marlene and the agency.
Act 2, Scene 2 is set in Joyce’s backyard, where two young girls, Angie and Kit, have built a shelter out of junk. They tease and challenge each other, and make a plan to see an X-rated film in town. Angie speaks in a blunt and monosyllabic manner, and vocalizes her desire to kill her own mother. Angie also reveals secret plan to visit her aunt (Marlene) in London. Later, Joyce (Angie’s mom) makes Angie clean her room before she can go to the movies. Angie returns wearing an old best dress that is slightly small for her. It begins to rain and Joyce and Kit run inside while Angie stays put. Kit comes out of the house and shouts at Angie to come inside, then goes down to Angie. Angie tells Kit “I put on this dress to kill my mother.”
Act 2, Scene 3 is set in the Top Girls Employment Agency on a Monday morning. Win and Nell have just arrived to begin work. They are drinking coffee and chatting about the men they dated or had affairs with over the weekend. Marlene arrives and Nell and Win applaud and whistle for her after being promoted over Howard, but Nell also indicates that she envies Marlene's success.
Later, Win interviews Louise, who is 46 and feels that it’s time to move on from her long-term job. Louise is frustrated at her lack of a personal life due to her sustained commitment to the job, and has watched as younger men are consistently being promoted to better positions while she is never considered. Win tells Louise the reality of the situation: that some companies may value her experience but they are more likely to hire younger men.
After the break, the setting reverts to the main office at Top Girls. Angie comes to see Marlene - who does not recognize her niece at first. Angie reveals that she has come to London on a one-way ticket without telling Joyce and will be needing a place to stay. Angie idolizes Marlene and starts asking questions about her job. While Angie is in Marlene's office, Mrs. Kidd enters. She is the wife of Howard Kidd, who lost the promotion to Marlene. Mrs. Kidd tells Marlene that the news has left Howard a nervous wreck and requests Marlene to give up the promotion - since Howard is a man and he has a family to support. Marlene brushes off Mrs. Kidd and her absurd request - and in response, Mrs. Kidd calls Marlene “one of those ballbreakers” and tells her she’ll end up “miserable and lonely.”
After the break, Nell is interviewing Shona, who claims to be twenty-nine and working at her current sales job for four years. Nell, impressed, suggests that Shona might a good employee for the Top Girls employment agency. Nell then presses Shona a bit on her current job and personal life, collecting details to present to potential employers. Shona delivers a far-fetched story about driving a company Porsche and staying in hotels on the company’s expense account. Nell realizes that Shona is lying and calls the interview a "waste of time". Shona finally admits that she is only twenty-one and has no experience.
After a scene break, Win enters the main office to find Angie seated at her desk. She introduces herself and praises Angie's aunt Marlene. They start talking and Win tells Angie about her professional trajectory. She offhandedly mentions getting married but indicates that her husband has been imprisoned. However, Angie falls asleep during Win's story. Moments later, Nell comes into the office and tells Win that Howard’s Kidd has had a heart attack. Marlene comes into the office and sees Angie asleep. Win tells Marlene that Angie aspires to work at Top Girls, and Marlene says bluntly, “Packer in Tesco more like.” Win says she thinks Angie is a nice kid, but Marlene says she’s “a bit thick…a bit funny” and that she’s “not going to make it.”
Act 3 is a flashback scene set at Joyce’s home on a Sunday evening, three years earlier - the last time Marlene visited Joyce and Angie in Ipswich. One of the gifts Marlene has brought is the dress that Angie wears in Act 1. Joyce grumbles that Marlene's surprise visit has caught her off-guard, and we learn that Angie has orchestrated the visit and invited Marlene without telling Joyce. In this scene, we learn more about Joyce and Marlene's past as the sisters begin sharing a bottle of whisky. At one point, Angie asks her aunt to tuck her in, and Marlene does.
When the sisters are alone, Joyce scolds Marlene for leaving town when she was younger and leaving Joyce to look after their mother and Angie, who is actually Marlene's biological child. The sisters continue to argue, and it comes out that Marlene got pregnant with Angie at age seventeen, but didn’t tell anyone about it until it was too late for an abortion. Joyce and her husband Frank offered to take the child, after being married for three years and having no children of their own. However, Joyce blames the stress of raising Angie for her subsequent miscarriage. Marlene and Joyce begin to argue about British politics, with Marlene taking the pro-Thatcher conservative side, and Joyce siding with the socialist left wing. The two change the subject and begin talking about their parents’ working class struggles and difficult marriage.
Marlene tells Joyce that she doesn’t “believe in class.” Anyone ought to be able to pursue their desires if they “have what it takes.” Marlene does not feel that she should be expected to help “stupid or lazy or frightened” people find jobs. Joyce thinks that Angie falls into the "stupid, lazy, and frightened" category, but Marlene brushes off her concerns. Joyce, meanwhile, expects Angie to have a wasted life so long as England is run by “them” meaning Thatcher’s conservative party. Joyce accuses Marlene of being one of "them". Later, Marlene tries to tell her sister to relax and says she did not mean everything she said. Joyce does not accept the gesture and holds onto her claims. She does not want to be friends with her sister - it is clear that their opposite life choices have driven a wedge between them. Joyce goes to bed.
Alone, Marlene sits wrapped in a blanket and pours herself another drink. Angie comes into the room and calls out “Mum?” Marlene says “Angie? What’s the matter?” and again Angie calls out “Mum?” Marlene replies, “Not, she’s gone to bed. It’s Aunty Marlene.” Angie then says “Frightening” and when Marlene asks if she’s had a bad dream and suggests things are fine now because she’s awake, Angie again says “Frightening” and the play ends.