The Doorbell and the Painkillers

Decades ago, possibly when I was in my teens, I read a short story about a doorbell and painkillers. It was during my science fiction/science fantasy days, I reckon. I've tried to find it, or some reference to it, on the internet, but without success. Stripped of its gothic atmospheric detail, the story, as I remember it, was this:

Whenever visitors rang the bell at the door of a remote, castle-like edifice, a strange, piercing sound arose, seemingly from far away - the bowels of the castle? - and an uncommunicative man-servant opened the door to them.

I forget the rest of the story, except that we discover the macabre and cruel secret of the working of the bell. - There are other people somewhere in the castle, underground maybe, or housed in a distant wing. They are in great pain. They are being cared for - nursed/doctored/spoken to solicitously - by person or persons who appear to care about their welfare. The treatment for their pain is pills - soothing pills - painstakingly concocted by their carers.

When they take the pills, the pills appear to help a bit; the pain subsides a bit. They perhaps allow themselves to relax a little. There is occasionally talk of becoming well enough to leave the castle, well enough to return home. But however they may appear to improve, and maybe to rest or sleep fitfully, there are terrible, anguished relapses, when, in concert, the patients scream in agony, clutching their stomachs, as though suffering the torments of the damned.

In brief, dear Reader, the pills they are being given contain tiny metal pieces, and the doorbell governs immensely powerful magnets, cunningly positioned. And when visitors ring the doorbell, the magnetism is engaged, and the tiny bits of metal within the innards of the 'patients' are pulled/attracted by that inhuman mechanism, and tear at the delicate, long-troubled tissues and nerves of those doomed victims of ill-conceived medication. And it is the sound of their screams that alerts the man-servant that there is someone at the door, someone waiting to be admitted... 

And the moral of this story is: Put not your trust in painkillers! They may cause you great harm...