Sister Isabetta silently endures Abbess Usimbalda’s abuse for a while, until she notices her odd headwear. Then she daringly suggests that Usimbalda “tie up [her] bonnet” before chastising others. A somewhat confused Usimbalda continues scolding, but when Isabetta repeats herself, the Abbess and the other nuns finally realize that she’s wearing breeches as a veil. The Abbess changes her tune, now “arguing that it [is] impossible to defend oneself against the goadings of the flesh.” Sister Isabetta and Abbess Usimbalda continue to see their lovers, despite the envy of the other nuns who, single, must “[console] themselves in secret as best they [can].”
Isabetta gets away with having a lover of her own, because her abbess is guilty of the same sin. This parallels the earlier stories where the young Tuscan monk and his abbot share the country girl (I, 4) and where Masetto finds himself in bed with all the nuns and the abbess (III, 1). It also emphasizes the themes of clerical and feminine hypocrisy. In the first case, as soon as she realizes she’s caught, Usimbalda disingenuously changes her tune; in the second, like Pietro’s wife (V, 10), she chastises someone else for the same sins of which she herself is guilty.