Script versus short story
This short story is one of Christie's longer endeavours, so it would have to be somewhat reworked to fit in a 50 minute time slot. Luckily, Horowitz more or less succeeds in maintaining the important plot points and character details. He does, however, make several significant changes. First, there is no letter from Chevenix to Poirot (he's called Chevenix here, not Chevenix-Gore). Instead, the two meet at an auction where they both bid on the same mirror. Second, Satterthwaite is removed and Hastings and Japp are added (in keeping with other episode in which characters like Satterthwaite, Goby and Arons are present). Hastings tags along on interviews and gets to discover certain points like "the first gong" some of the guest thought they heard. Third, Hugo Trent makes furniture here (very much in Poirot's style) and is upset because he can't get the financial backing from Chevenix. Lake (John Lake in the adaptation) has become an architect who has persuaded Chevenix to invest in a development project. This also allows for Poirot to be involved in the case at an earlier stage, because Chevenix invites him down to find out if he is a victim of fraud. Eventually, this leads Poirot onto a red herring at Northgate Development, the deserted building Lake has used for his fraud (leads to a somewhat dramatic rescue scene!). Fourth, several characters are removed, including Colonel Bury, Mr. Forbes, Godfrey Burrows and the doctor. Fifth, Ruth's background, with the unknown mother, is more obvious here. Sixth, Chevenix is something of an eccentric art historian, and not a 'Sir', but his interest in family and family history is still present. Miss Lingard works for him as a research assistant - they are preparing a book for the Museum of Modern Art (an important addition, because a painting leads Poirot onto the murderer). Finally, the murderer used a champagne bottle rather than a paper bag to create the illusion of a shot - and she even tries to convince Vanda that she killed her husband by appealing to her superstitious nature. All in all, though, the adaptation is largely faithful and the end result is a dark episode of the series.
Directing, production design, locations, soundtrack
Farnham's direction is competent, with good use of the locations and the occult angle to the proceedings (Gunning's music similarly plays on this element). The house used as Chevenix's house is 'Marylands' in Surrey
Characters and actors
The most memorable guest actor here is Iain Cuthbertson (Gervase Chevenix), but Jeremy Northam (Hugo Trent) and Richard Lintern (John Lake) should be familiar to many. The latter would make another appearance in Mrs. McGinty's Dead.