Hatem said that when casting the part of Alva Keel, a mysterious person was necessary for the role, "someone who would draw Paul away from the Church and bring him into this strange world of paranormal investigation". Donald Sutherland was an original casting idea, because the producers originally wanted someone who was around the same age as Hector Elizondo, to persuade Paul to leave behind one father figure and follow another. However, after many people auditioned, the producers took note of Angus Macfadyen's ability to without speaking, like Ulrich, portray intensity and mystery. The casting of Macfadyen gave the producers the idea of instead of following a new father figure, Paul Callan would join a group based on "brotherhood", "someone who was more of an age contemporary with Paul".