Once upon a time and a very good time it was there was a moocow coming down along the road and this moocow that was coming down along the road met a nicens little boy named baby tuckoo. . . .

Stephen's father, Simon Dedalus, tells his young son an old-fashioned children's story. Simon begins the story with the traditional "[o]nce upon a time" and uses babyish words like "moocow." With his childish yet vivid imagination, the young Stephen identifies with the story's character, "baby tuckoo." We see some of Stephen's impressions of early childhood: the cold bedsheets, the pleasant smell of his mother, the applause he receives from his governess Dante and his Uncle Charles when he dances to the hornpipe.

At one point, Stephen expresses his intention to marry the young girl, Eileen Vance, who lives next door. Eileen happens to be Protestant, however, and in response to his Catholic family's shock, Stephen crawls under the table. Stephen's mother assures the others that he will apologize, and Dante adds a threat that eagles will pull out Stephen's eyes if he does not apologize. Stephen turns these threatening words into a ditty in his mind.

The story shifts to Stephen's experience at Clongowes Wood College. Stephen watches other boys playing ball but does not participate himself. The other boys are mildly antagonistic toward Stephen, asking his name and questioning what kind of a name it is. They ask about Stephen's social rank and want to know whether his father is a magistrate. In class, Stephen is forced to compete in an academic contest in which the opposing teams wear badges with red or white roses—emblems of the noble York and Lancaster families from English history. Stephen does not perform well, and wonders whether green roses are possible.

Stephen tries to study, but instead meditates on himself, God, and the cosmos. He examines his own address written in his geography textbook, beginning with himself and listing his school, city, county, country, and so on in ascending order, ending in "The Universe." Stephen wonders whether the different names for God in different languages refer to the same being, and concludes that the names are in fact all the same being. When the bell rings for night prayers, Stephen addresses God directly. The chaplain's clear and formulaic prayer contrasts with Stephen's own quietly murmured prayer for his family's well-being. Dreading the cold sheets, Stephen climbs into bed and shivers. In a feverish vision, he thinks of a big black dog with bright eyes and of a castle long ago.

Later, various people ask whether Stephen is sick, and we find out that his sickness is probably the result of having been pushed into the "square ditch," or cesspool, the day before. Wells, the boy who pushed Stephen, is the ringleader of the school bullies. Wells again tormented Stephen by asking whether Stephen kisses his mother. Stephen was unsure whether to answer yes or no, and the boys laughed in both cases anyway.