I think it's sometimes fun to watch mysteries that don't have murder attached for a change.Yes, one thing I've been struck with in rewatching these Hardy Boys/ Nancy Drew Mysteries is how frequently atmospheric they are. And the opening credits set the mood nicely, with that spooky theme and the use of the blue hardback book covers mixed with live action.
I've been meaning to check out that Mickey Mouse Club "Applegate Treasure" Hardy Boys serial. I think the complete run is available on YouTube. I think the Kirk and Considine are bit young for my image of the Hardy Boys, but I'm curious to give it a look.
Remember when many of us old timers watched the MMC serial we were in that age group and it was the only game in town. (Besides nobody sung in them)