'Casting the Runes' must be MR James most influential ghost story. It's been adapted from almost any medium you'd care to mention. I wouldn't be surprised if there's a musical out there:
'These letters are quite runic
They're not Latin or Punic'
And who could forget the showstopping:
'I was shaking like a willow
When I felt that mouth under my pillow'
None of which is relevant top 'The Hex', a BBC radio play you can listen to at the excellent Zombie Astronaut site. It's conventional enough, but a well-paced and enjoyable adaptation. It would, I think, have made a good TV play.