Juno and the Paycock takes place in the tenements of Dublin in 1922, just after the outbreak of the Irish Civil War, and revolves around the misfortunes of the dysfunctional Boyle family.Near the end of the act, one of Jack's relatives dies, and a schoolteacher, Charles Bentham, brings news that the Boyles have come into a large inheritance; Bentham notes aloud that the will names "John Boyle, [my] first cousin, of Dublin" as one of the beneficiaries. Overjoyed with the news, Jack vows to Juno to end his friendship with Joxer and change his ways. Act II
A mere two days after receiving Mr Bentham's news, Jack has already begun flaunting his newfound wealth by purchasing a new suit, new furniture, a gramophone, and other luxuries on credit, in anticipation of receiving the inheritance. The Boyles throw a party and invite Bentham, who is courting Mary. Joxer is present, Jack having already forgotten his vow to break off contact with him, and Mrs Maisie Madigan, a neighbour to whom Jack owes money, shows up after having been invited in Act I. During the party, Robbie Tancred's funeral procession passes the tenement, but the Boyles and their guests halt their carousing only when Tancred's grieving mother stops at their door. Juno goes out to offer support to Mrs Tancred, who delivers a monologue mourning the loss of her son and praying for an end to the war, but Jack selfishly ignores her suffering. Act III
Two months later, Bentham abruptly ceases all contact with the family and abandons Mary, who, it is revealed, is secretly carrying his child out of wedlock. While Jack is sleeping, Juno takes Mary to the doctor. Soon after they leave, Needle Nugent, the local tailor, storms into the flat and repossesses Jack's suit. Then Mrs Madigan arrives, demanding repayment of the loan she gave Jack; when he refuses to pay, she takes the gramophone as recompense. Joxer (who was present for both incidents, and did nothing to help) needles Jack about rumours that the inheritance is not forthcoming; this soon devolves into an argument during which Joxer openly mocks Jack's fortune as fraudulent. While Johnny upbraids his father for embarrassing the family, Juno returns alone and delivers the news of Mary's pregnancy. As Juno pleads with Jack to use the leftover money from the inheritance to move the family to a different city, he angrily reveals that they will receive nothing due to an error Bentham made while drafting the will (he failed to include the beneficiaries' names, referring to Jack only as "[my] first cousin").