The play begins in a hedge-school in Baile Beag with Manus trying to teach Sarah to speak. The school is run by Manus' father is the schoolmaster and the hedge-school and teaches the students to speak Irish, Latin and Greek; not English. Owen, the younger brother of Manus returns to his home town and enters the school to announce he is working for Captain Lancey and Lieutenant Yolland in creating a map of the land. Owen is specifically helping Yolland to translate the Irish names of locations in the village in order to help him create an anglicized version of the placenames. Owen doesn't see this as any great disturbance and carries about his work.
We learn that Manus is in love with Maire, but she won't marry him due to his lack of having any proper job, money, and standing in society. Manus cares for his father, Hugh, who is constantly inebriated, and won't apply for a job at the same school his father has applied to teach at. Maire can't understand why he must live in his father's shadow his entire life. Hugh is granted to position of headmaster at the school, and two men arrive in the village to offer Manus a job teaching at a distant school. They will pay him, give him board, crops and animals--all of the things he believes he needs for Maire to agree to marry him. But, Maire has invited Yolland, who has fallen in love with Ireland as a country, to come to a dance with her and despite their inability to speak one another's language kiss after the dance.
Manus finds out about the kiss, and the next day Yolland has gone missing. We learn that Irish twins, the Donnellys were seen coming to the dance and they are known to be violent. It is assumed that they kidnapped Yolland or killed him. Manus, who is heartbroken by the betrayal of the kiss decides to leave home and not accept the teaching job. Captain Lancey declares that if Yolland isn't found the English army will within 24 hours kill the villager's livestock, then destroy their crops and level their homes until someone confesses to Yolland's whereabouts. Owen decides to leave to join the resistance and the play ends without resolution to where Yolland is, and Hugh, who is drunk, recites the opening of Virgil's Aeneid.