The novel My Soul to Keep tells a surreal tale of what might happen if mortal and immortal worlds were to collide. The book, which tells the story of an immortal man married to a mortal woman, deals with the themes of loss and death. Another idea that is toyed with in the novel is a question of whether evil and good can exist simultaneously as David murders and lies in order to protect his family and himself from his past. Even though David tries to perform a ritual to keep his wife, Jessica, and daughter, Kira, with him forever, he loses them both.

David, who is also known in the story as Dawit and Seth, has undergone a Life Ritual with Jesus Christ's blood to give him immortality. Khaldun, who went through the ritual because he was "greedy for life" invites other men, including Dawit, to join him in immortality to develop a habitat of scholars in an Ethiopian city called Lalibela. Instead of staying in the city, however, David chosoes to spend his time among mortals, taking wives and having children until he becomes tired of watching his families become old and die or being taken away from him by the Searchers.

He decides to slowly introduce his current wife, Jessica, to his true identity in the hopes that she will agree to go through the ritual and live forever with him. As David is revealing his identity to her, Jessica is doing some research on her own and, with her sister's help, learns that David's blood has amazing healing properties. In the process of protecting Jessica from learning about his past before he is ready David does horrible things including killing her great-uncle and her co-worker. When Jessica finally realizes what her husband has done in order to cover his secret, she feels angry and betrayed, but realizes she still loves him.

In order to keep from having to lose his wife and daughter, David decides to perform the Life Ritual on the two of them. Because he believes that his Life Brothers are trying to kill Jessica and Kira, David tries to quickly go through the ritual in a hotel room. Although David manages to pass on immortality to Jessica, he winds up losing her. Jessica, however, uses her immortality and special powers to help others.