The popular detective Dr. Morelle played by Valentine Dyall is our protagonist who stars in the Case Of The Missing Heiress. The story is told in flashback and in this case a bad idea because we know that the good doctor's assistant Julia Lang has had no harm befall her. Not good especially for those not familiar with the character on British radio who knows that she would have to be back for next week's episode.
Morelle fancies himself Sherlock Holmes and he has the weapon of hypnotism at his command unlike Holmes. He also has Lang as a faithful scribe of his adventures, but Watson would have walked out if Holmes had ever treated him the way that Morelle treats Lang.
In any event Lang gets a call for help from an old friend who is being kept prisoner by her stepfather and unable to see her boyfriend. The friend stands to inherit a considerable fortune, but the friend after making the call disappears. Stepfather Phillip Leamer doesn't want publicity and neither does boyfriend Peter Drury.
We find out that the butler didn't do it when butler Hugh Griffith turns up dead as well and a frantic Lang calls Dyall for help. Of course when he comes to Devonshire where the spooky estate of Leamer is located, he solves the whole mess.
Griffith is best in the cast with his performance of a slightly daft butler who walks an imaginary dog. But the film itself looks like it was slapped together rather quickly no doubt to take advantage of the radio show's popularity.