In this scene, Curtis, a servant of Petruchio, is told certain events that have transpired between his master and his new mistress, whom he has not yet met, but of whom he has heard that she is a "shrew." However, from what Grumio relates about what has happened, especially on their journey back to Petruchio's home together, this supposed infamous "shrew" does not seem shrew-like at all, but rather dominated by her cruel husband, who seems to play the role of "shrew" in their relationship. Note what Grumio tells Curtis about what their master did to their new mistress:
...thou shouldst have heard how her horse fell and she under her horse; thou shouldst have heard in how miry a place, how she was bemoiled, how he left her with the horse upon her, how he beat me because her horse stumbled, how she waded throguh the dirt to pluck him off me, how he swore, how she prayed that never prayed before...
It is interesting to realise that Katharina, thanks to the behaviour of her new husband, actually becomes the protector of his servants as she tries to shield them from his irrational behaviour. Katharina does not appear the shrew in this scenario at all, which is why Curtis comments that "he is more shrew than she."