Since leaving the hospitality industry to pursue a career in writing, K.W. Callahan has written books on a variety of subjects as well as penned articles for numerous print and online publications. Before his work on the Systemic series, K.W. authored The M.O.D. Files: The Guest Who Stayed Over, a murder mystery set within the confines of a landmark Chicago hotel, and Palos Heights, a suspense thriller that follows four college students on a weekend bike trip that takes a dark and deadly turn.