I wasn't expecting much more than some light disney badly acted time waster but this definitely has some things going for it.
Hayley Mills is the shining star of it all. Her energy and commitment to her character, which may well just be her being herself carries the movie all by itself. She's charming, interesting, clever and funny all at once.
Dean Jones is focused and interesting in his own way as were many of the characters.
The plot is secondary to their characters, it's not a nothing idea but it's not edge of your seat fare either, but that doesn't matter as it's just fun watching the actors do their thing.
The 2 baddies were surprising chilling, they obviously didn't get the memo this was a Disney movie. Frank Gorshin (AKA Mr Riddler) was quite scary, channeling any number of mob thug movies as was his partner in crime.
Roddy Mcdowell was creepy but performed his roll, and it was great to see Richard Eastham doing some fast comedy. There was a bit of that. Witty fast dialog.
Definitely not fluff, it was fun and funny.