The Human and the Faerie became good friends and Arthur often discussed things with Thimbletack during his work with the Field Guide, among them an eventual transformation from Boggart to Brownie (which Thimbletack doubted). When Arthur became prisoner of the Elves in September 1935, his wife Constance died shortly after and his daughter Lucinda ended up in mental But when the siblings created a new home for Thimbletack, he transformed from the mean Boggart back to the helpful Brownie he used to be. He returned the mice to Simon and warned the Grace children for how dangerous the book could be.