Raphael Cain is a 17th century Dutch sailor "blessed" with immortality by the father of his wife. When demons kill her, Raphael swears an oath to walk the earth as long as there are demons left to die. He makes the acquaintance of a young man, Goodwin, who he takes on as his squire. Now in the modern day, Raphael and Goodwin join forces with parapsychologist Dr. Sara Beckman to battle demons wherever they may find them.