Script versus short story
Some changes have been made on the journey from short story to film. Most importantly, the 'impressario' Henry Reedburn becomes the owner and producer of a 1930s film studio, and the 'dancer' Valerie St. Clair becomes his leading actress. A director called 'Bunny' is added to the mix, and he's an old friend of Hastings's, so Poirot and Hastings visit the film set of the latest picture. Also, there's an older actor struggling to adjust to the era of the 'talkies' added to increase the list of suspects once the murder is committed. Prince Paul is here an old acquaintance of Poirot, who has helped his family in the past. He also funds most of the film Valerie stars in (which is why he's at the set on the day of their visit). Consequently, instead of asking Poirot for a consultation, he calls his old friend up at night, asking him to look into the business. Chief Inspector Japp is also introduced, having been called out to a report of "disturbance" at Mr. Reedburn's house (would a Chief Inspector be called out to such a minor affair? Probably not). Finally, a group of gypsies in the neighbourhood of Mr. Reedburn are included, a group that Reedburn has been trying to get rid of (again, increasing the number of suspects). Certain parts have been moved around a bit, but apart from the above changes, the adaptation stays true to its source material. One insignificant change that puzzles me is the fact that Poirot seems to get access to the scene of the crime both without Japp's help and the help of Paul (whose name he has promised to keep out of the business to avoid scandal). I just find it unlikely that he would be let in to these houses, even if he introduced himself as the great detective, acting in the interests of St. Clair.
The ending (both in the short story and the adaptation) has puzzled many Poirot fans. It's one of the few instances in which Poirot lets the culprits go. Though not as serious as murder, since this is essentially an accident, it's still difficult to understand why he would let them get away with it - when he's so hard on other culprits. Oh well, we can't really blame the series for that, though, since this is entirely Christie's choice.
Directing, production design, locations and soundtrack
Renny Rye directs this tale most competently, and he makes excellent use of the wonderful sets. Also, the sequences from the mock-1930s-film seem highly believable. I'm sure I could have been fooled if I saw that outside the context of the adaptation! The main locations here are a section of the Hoover building in Perivale, Middlesex (doubling as Parade film studios here - and as Farley's factory in The Dream!), and High & Over in Amersham, Buckinghamshire (doubling as Mr. Reedburn's house). See Joan Street's website for photos. The soundtrack is by Christopher Gunning, but it's not one of his most memorable.
Actors and characters
There isn't much character development for our main stars in this one. Hastings gets to comment on a car (owned by his friend Bunny - I find it interesting how many friends they seem to have added who could believably have been in the army with Hastings), and we get to know that Poirot has important friends and connections (but we already knew that, really). The main standout of the guest actors is Niamh Cusack as Valerie St. Clair. She certainly fills the role of a screen celebrity.