Cork and Marriott venture into the countryside to investigate the murder of Lady Langford.  Her husband, General Sir Gerald Langford (Brewster Mason), is a distinguished old solider, whilst his late wife was much younger (and had previously been an actress).  After viewing where the body had been found the pair venture to Langford’s palatial house and begin to peel away the layers of this intriguing mystery.

Cork’s check suit (presumably it’s his country wear) is a sight to behold.  But whilst his appearance is a little distracting, Cork’s analytical skills remain just as sharp in the country as they are on the streets of London.  Sir Gerald is convinced that his wife was killed by a mysterious madman, but Cork is quick to contradict him – he believes that the murderer will be found much closer to home.  A little later Cork outlines his detective’s philosophy to Marriott. “You have to cultivate a mind that traps details like a spider’s web snares flies. And always work on the assumption that things are never quite what you think they’re going to be.”  Rather delightfully he breaks off from his monologue to wonder if he’s becoming pompous in his old age, telling Marriott that if so then Bob has his permission to boot him up the backside!

The General is wheelchair bound, so that seems to eliminate him, but he has a house-guest (the mysterious Jean-Pierre Ducane) who seems a likely suspect.  British-born Robert Arnold, playing Ducane, sports a very broad French accent.  British actors playing every nationality under the sun were very common during this era of television, but if you think he’s going rather over the top there’s a clever twist later on which explains why.

Brewster Mason is rather odd casting as Langford.  The General is presumably supposed to be in his sixties, but Mason was only in his early forties when this was made.  A fake beard and wig aren’t really enough to sell the illusion that this is an elderly man, especially when the camera favours him with close-ups that show his unlined face.

Director Anthony Kearey adds a few flourishes to the production.  A particularly memorable shot is that of Ducane, as seen though the barrel of Langford’s rifle.  Apart from a few brief scenes elsewhere, the bulk of the story takes place in Langford’s house (which is attractively decorated with mementos from the General’s time in India).

So this is effectively a country house murder mystery – and in time honoured fashion it concludes with Cork gathering all the members of the household together before revealing the murderer’s identity.  This was Jon Manchip White’s sole writing credit for Cork, which is a pity as The Case of the Knotted Scarf is a very decent murder-mystery with an unexpected ending.  Since there aren’t that many suspects it’s possible to have a stab at working out who the murderer is (although I have to confess that I didn’t get it right!).