In 1956, when she was only four years old, Karen Heasley died on the operating table while having her tonsils removed. While she was dead, she traveled through a dark tunnel and felt a peace she hasn't felt since. It would be twenty years until she discovered the work of Raymond Moody and understood she had had a Near Death Experience. It also explained why she was sensitive to the spirits around her.

One hundred years before Karen's birth, in 1907, Lydia Marquette was the first medium to stand up for her rights to practice Spiritualism in New Castle, Pennsylvania. After suffering through a fortunetelling trial, she went on to help found a new religion in the flourishing steel town. She joined with the Johns family and Agnes Guthrie to become leaders who changed the culture of the city. Blessing from Agnes is based on true events. It interweaves the struggles of the early Spiritualists and Karen's efforts to remain "normal" in an old western Pennsylvania steel town. It follows her as she discovers her true calling and rids herself of the expectations of her community, church, and family to become a Spiritualist medium. The fight is not always easy, but like the Spiritualists who lived in New Castle one hundred years before, she is determined to succeed.