Ellery Queen1975

Ellery Queen:
I've got it. Scene 231A: that's the clue. I know who killed Gilbert Mallory and Mike Hewitt. You know who killed them? Was it Mallory's wife, or his current mistress, or was it the director, the prop man who hated him, or was it somebody else? And why was Hewitt, the stunt man, killed. I'll tell you one thing: my dad was right when he said the killer made a mistake. But when - and what?