Alison Sedge was once a pretty young fieldmouse. When she received her mousebrass, The Sign of Grace and Beauty, she became especially aware of this. She began teasing the boy mice and took great care of her appearance.
But despite the fact that she and Jenkin Nettle had stopped going together for this very reason, it was clear that she still loved him.
When Audrey Brown came to Fennywolde, Alison became very jealous because Jenkin seemed to take a liking to her. After Jenkin had been killed by Mahooot the owl, Alison blamed Audrey for what had happened. Even after she had realized that the spirit of Jupiter was behind everything, she still hated Audrey.
Ever hurt over the death of Jenkin, Alison went mad and stopped taking care of herself. Her appearance became so frightful that some even considered her to be a witch.
When the strange black squirrel Morella arrived in Greenwich, it was noted that she looked very much like the young Alison. The connection between the two has not been revealed as of yet.