Houdini's Ghost is loosely based on the Dalziel and Pascoe book 'Good morning, midnight' by Reginald Hill, and is one of fewer episodes based on a book from the original series.
(DC Lateef had called DI Pascoe to the scene, but Dalziel turns up on his day off.) DC Lateef: How do you know something was going on Sir? Dalziel: I was dusting my crystal ball.