We only hear of Theodoric's mother in the early part of the story, but she evidently made a deep impact on her son.
The narrator describes her as an over-protective mother who coddled Theodoric because she wanted to protect him from the harshness of life. She is described as "fond" of him and as keeping him "screened" from life. As the narrator puts it:
When she died she left Theodoric alone in a world that was as real as ever, and a good deal coarser than he considered it had any need to be.
This over-protection, in other words, has not served Theodoric well. He is ill prepared for the harsher side of life and is annoyed when he has to go to the stable with the vicar's daughter and help her harness the horse to the buggy that is to take him to the train station to go home.
The over-protected Theodoric is later mortified when he realizes a mouse from the stable has gotten into his clothes. He is sharing a train compartment with a woman, and the idea of having to partially undress to set the mouse free is very uncomfortable to him, because he fears his compartment mate will be embarrassed. However, his desperation to be free of the mouse causes him to undress anyway.
Only too late does he realize the woman is blind. However, much of Theodoric's agonized mortification could have been spared had he not been so over-protected by his mother.