Not only did William Peter Blatty write the second sequel to this film, he directed it as well
This is the only Exorcist film not to be distributed 
theatrically by Warner Bros., though Warner Bros. .... William Peter Blatty, 
although initially having no desire to write a sequel to The Exorcist, eventually 
came up with a... [DOC] [TLE] The Exorcist (film) - Wikipedia [PAR] The Exorcist is a 1973 American supernatural horror film directed by William 
Friedkin, adapted by William Peter Blatty from ...