Story rewrite- horrible. Instead of looking for WWII spies, the Beresfords are on the trail of a stolen atomic bomb and a Russian agent. Albert is a certifiable genius instead of a hapless doorman, Tommy is a bumbling fool who is lucky not to be dead; Tuppence is an irritating, silly woman who pushes Tommy around; Derek and Doreen? Gone.. MIA. Instead there's "George" age unknown. Betty Sprot has been forgot and her mother is a flirtatious dimwit instead of devoted mother. No Goosey Goosey Gander, either. Mrs. Perella and her daughter have evidently been merged; Carl is an adolescent biker. Story DULL as DISHWATER...despite frequent and unexplained attacks on the protagonists. UGH!
Casting: PUHLEEZE. Neither of the principle actors bears any semblance at all to the original characters. Tommy doesn't even have red hair! Roy Marsden's is the only credible performance.
Setting: The 50s were dull and so are these sets. The Beresford wallpaper is god awful. The 40s were a much more glamorous setting.
Seriously, Christie stories work best when they follow the story she wrote. The adaptation of N or M? is even worse than the many unspeakably bad Marple rewrites. AC must be rolling in her grave.