Father Donald Frank Callahan is a fictional character created by Stephen King. He originally appeared in the 1975 novel 'Salem's Lot and later The Dark Tower, appearing in The Dark Tower V: Wolves of the Calla, The Dark Tower VI: Song of Susannah and finally The Dark Tower. He is at first an alcoholic with a troubled faith, but he seems to find his peace in The Dark Tower novels, and his faith is restored.