Who Owns Alfred Hitchock Show Script?

Dear Rich: I'm working on a script that is very loosely based on a radio play by a dead author; it was remade into an Alfred Hitchock show and I tried to track down the owner via NBC, who aired the show in the 60s, to no avail. So do I go through the family of the dead author? Would his estate own it (he wrote successful movies as well, so he's sort of a respected screenwriter) The NBC folks weren't really sure who owned the show, and the play was originally on an old radio play from the 30s or 40s, presumably all of the producers are dead and the show seems to be public domain ("Suspense") but I'm not totally sure if the story is since it got reproduced for TV. My story would digress substantially but has a similar set up and theme, although my characters are very different. How should I proceed? We're not sure we agree with you that the source material is public domain. The Alfred Hitchcock Presents episode does not appear to be public domain (only one of his TV episodes seems to have slipped under the PD trapdoor). The status of the work is also unclear because you are dealing with issues regarding derivative works. That is, there may be separate copyrights in the underlying story (based on the radio play) and in new material added to the teleplay.  (This chart provides a breakdown of the AHP teleplay writers and story creators.)
Tracking the owner -  the Rear Window problem. By a strange coincidence, your problems in determining ownership may be compounded by a Supreme Court ruling dealing with another Hitchcock work. As you can see from reviewing the case, ownership of older stories-turned-to-screenplays can often be murky. If you had sufficient resources you could engage a copyright research company to provide a full report on the ownership status. (Here's how to review public records on your own.) We think you'd have a far easier time modifying the plot and characters so all that remains are the general ideas and perhaps the basic plot twist -- sort of like the way Brian DePalma's Obsession is based on Hitchcock's Vertigo.
Need any theme music? By the way, you're free to re-record and use the Alfred Hitchcock Presents theme as that was lifted directly from a public domain composition (theme starts at about 38 seconds in) On a related note, here's a summary of the public domain status of Hitchcock's films.