The screen rights to Levin's stage play Deathtrap were purchased by Warner Brothers less than a month into its original Broadway run, for a record-breaking 1.5 million dollars. Levin had initially contemplated writing the screenplay himself, telling 1978's Christian Science Monitor:
Ultimately, Levin passed on writing the screenplay himself. Warner's contract required that they wait four years before releasing their film version (an unfathomably long stretch for a standard play) – and indeed, weeks after that waiting period expired, the movie hit theaters. And a mere three months later, Deathtrap's four and a half year Broadway run came to an end. (At that time, the existence of a less expensive movie ticket alternative to the far-costlier Broadway equivalent was a virtual death sentence for any play.)
No fault can be found with the 1982 film's Michael Caine/Christopher Reeve-led performances, its direction, or its baroque-flavored Johnny Mandel musical score. Levin was not however enamored of screenwriter Jay Presson Allen's newly-imagined opening and ending scenes, telling legendary talk-host Larry King in 1991:
Moreover, Levin was not thrilled with Allen's toning-down of the comedy half of his comedy-thriller. Allen told the New York Times:
“Ira Levin's script is very, very clever and a little profligate. He gives you six laugh lines in a row. And reversal, reversal, reversal. When you take his script and go down the page, there's feed line, laugh line, feed line, laugh line. A film audience won't buy that. There must be reality about the situation.” ¯\_(ツ)_/¯
Deathtrap was one of the inspirations for 2019's Knives Out.