At the start of "Serch Bythol", Theresa is a painter of birds and flowers. Many of Susan's weaknesses are still within her as Theresa. Readers first see Theresa when she is giving her marriage to Gerald Pierson one more chance by starting a new life with him in Yorkshire, England. Theresa had been having an affair with a younger painter and ended it for the sake of her family.
David and Theresa have a preternatural closeness from their incarnations as Daniel and Susan. Theresa is a source of strength and love for David, but her karmic involvement with his demons, and her fear of losing him the way she lost Daniel, sometimes paralyzes her.
Theresa is an empath who tries to help everyone who comes into her life. This sensitive nature often makes it difficult for her to live with her brash, outspoken husband, Gerald.
Upon moving to the Yorkshire farmhouse she is immediately affected by Nathaniel's spirit and the familiarity of Beak's End. Theresa does not recall her past life like David soon does, but learns many things from her interaction with Nathaniel that eventually form a picture. In order to help his tormented ghost, she is forced to become increasingly distant from her husband and sons, and even from this world itself. This is a cause of tremendous concern for her family, but Nathaniel will never hurt her. She gradually comes out of this a changed woman and another kind of artist. While helping Nathaniel, she painted a series of works depicting his anguish. David and her mother, Eleanor, understand that Theresa carried tremendous guilt about Nathaniel's downfall from her life as Susan, and that she had to go wherever was necessary to help him get back on his true path.
By the end of the book, Theresa becomes the artist she always wanted to be, the one whom David envisioned. Even though Nathaniel's spirit peacefully went on, in her heart, he will always be her greatest love.
To be filled in.