Dublin, 1921. A group of neighbors meet on the street corner and lament their lot
(“We’re Alive”). A troop of English soldiers marches through in pursuit of revolutionary Robbie Tancred. In the next scene, Mary and Johnny Boyle learn that Tancred was killed. Their mother, Juno, enters. Johnny, who has lost a hand fighting the British, tries to avoid talking about the death of Tancred; Mary expresses her independence and discontent with her life (“I Wish it So”). Juno reproves both for their lack of pragmatism and the demands they make on her (“Song of the Ma”). Back on the street, a group of men steers a bill collector away from the Boyles’ home; we learn that Jack, Juno’s husband, isn’t working. Shift to the local bar, where Boyle and his friends Joxer and Sullivan are roistering (“We Can Be Proud”). Boyle celebrates his gift of the gab (“Daarlin’ Man”). In the park, Mary meets Jerry, a prospective suitor, but she makes her lack of interest clear. He is disappointed (“One Kind Word”). Boyle and Joxer return to Boyle’s apartment.
Juno enters; they try to convince her that they have found work, but she doesn’t believe them. She tells Boyle that Jerry is searching for him. Jerry enters to tell him that a job is available, whereupon Boyle feels pain in his legs. Juno scorns his laziness (“Old Sayin’s”). Juno exits and Joxer returns; Boyle and Joxer reminisce (“What Is the Stars”). Juno enters with Mr. Bentham, who reveals that a relative of Boyle has died and left him several thousand pounds. On the street, the neighbors discuss the Boyles and their good fortune (“Poor Thing”). In the next scene, Bentham and Mary sit in the park and reveal their feelings for each other (“My True Heart”). Back on the street, two IRA men are looking for Johnny Boyle. They exit, and Juno and Boyle enter wearing new clothes. The neighbors congratulate them, and they congratulate Mary and Bentham (“On a Day like This”).
Boyle and Joxer enter the Boyles’ apartment with a new gramophone. Juno worries about the rate at which Boyle is borrowing against the inheritance, which has not come to them yet. Mary and Bentham enter; Bentham explains that it will take time for the money to become available. Boyle asks Mary to sing (“Bird upon the Tree”). Other neighbors appear for a party (“Music in the House”). Then Mrs. Tancred enters, on her way to church for her son’s funeral.
The partygoers sympathize with her grief and laud her son’s heroism (“Hymn”). An IRA man orders Johnny to attend a meeting the next day, suggesting that he knows who informed on Robbie Tancred. The neighbors gossip in the next scene, speculating that Bentham has deserted Mary and the inheritance isn’t real (“Poor Thing” reprise). In the Boyles’ apartment, Mary tells Juno Bentham won’t be back; Juno tries to reassure her. She insists that Mary visit the doctor. Once they leave, Joxer and the tailor enter; the tailor wants money from Boyle. Boyle doesn’t produce any, so the tailor takes back his suit. Boyle and Joxer quarrel and Joxer exits in anger. Juno returns and reveals that Mary is pregnant. Boyle rages while Juno defends Mary. Then Boyle reveals that there will be no inheritance. He says Mary must leave; Juno says she will go with her. As Boyle heads for the pub, the IRA men come for Johnny and take him away. In the next scene, Mary sits quietly in the park (“For Love”). Jerry offers himself to her again but retreats when she tells him she is pregnant. In the next scene, Juno learns that Johnny has been killed for being an informer (“Lament”). Juno and Mary resolve to leave Dublin for the country as Boyle and Joxer get drunk at the pub.