Laurie is lying in his hammock being lazy when he sees the March girls leaving their house, carrying a variety of strange things. Laurie thinks they are having a picnic without him and feels left out. He goes after them to see what they're doing, and to give them the key of the boathouse if they want it.
Coming over the hill, Laurie sees the four girls sitting under a tree and working busily. Meg is sewing, Amy is sketching, Jo is knitting and reading aloud, and Beth is sorting the pinecones that she uses to do crafts.
Laurie isn't sure whether he should go away quietly and leave them alone. Jo and Beth want to let him join them, but Meg says that he has to do something – this is a "Busy Bee Society" and nobody is allowed to be idle.
Laurie takes over reading aloud from Jo. When he finishes the story, he asks what they're doing.
Meg and Amy are still worried that he'll make fun of them, but over their objections, Jo explains about the "Pilgrim's Progress" game. The girls have stayed busy all summer as part of "carrying their burdens" in the game, and sometimes they come and work on the hill and pretend it is the Delectable Mountain from the story.
The girls talk about their hopes for the future and allude to their hopes of going to Heaven in the afterlife. Beth longs to see Heaven, and Jo and Laurie talk about how hard it is for them to be good.
After a pause, Jo and Laurie begin talking about their earthly dreams and hopes – their "castles in the air." Each of them describes his or her own "castle in the air."
Laurie's dream is to travel the world, then live in Germany and be a famous musician.
Meg's dream is to be the mistress of a wealthy mansion. Laurie and Jo tease her about wanting a master for the mansion, too, and maybe children.
Jo says that she would have a stable full of horses, a house full of books, and be a famous writer. She wants to do something amazing before she dies.
Beth just wants to stay at home and take care of the family.
Amy wants to go to Rome and be a famous artist.
Laurie comments on the fact that they are all ambitious. Jo suggests that, in ten years, they should get together and see how their real lives compare to their dreams.
Laurie talks about his grandfather's plans for him and how much he dislikes them. Mr. Laurence wants Laurie to go to college, then be a merchant importing tea, silks, and spices from India. Laurie is going to go to college, but hopes that after that his grandfather will let him do what he wants.
Jo thinks Laurie should run off and have adventures. Meg rebukes her and tells Laurie he must do what his grandfather wants. Meg advises Laurie to be as good as Mr. Brooke.
Laurie asks Meg what she knows about Mr. Brooke. Meg says that she knows he looked after his mother while she was dying, works hard, and is kind.
Laurie says that Mr. Brooke really likes the March family and was flattered to be treated well by them. They treat him just like Laurie and don't make a big deal of the fact that the Laurences are wealthy and he's just their servant. Laurie says that one day he'll do something to help Mr. Brooke get along in life.
Meg says that Laurie could help Mr. Brooke now – by being a more diligent student! She can always tell how Laurie behaved by watching Mr. Brooke's face when he leaves the Laurence house.
Laurie is a little bit offended at Meg's nosiness and she apologizes to him. He apologizes also, saying that it's good to have the girls point out his flaws in a sisterly way.
Laurie continues to help the girls with their tasks until they hear the tea bell ring at the March house. The girls pack up their stuff to go home for the evening meal.
Laurie asks if he can join them again, and Meg says yes. Jo says she will teach him to knit socks.
That evening, Mr. Laurence sits listening to Beth play the piano, and Laurie watches them. He realizes that he is all his grandfather has, and resolves to forget his castle in the air and be a dutiful grandson.