I discovered this series on '70s American public television by accident while channel-surfing (or whatever we called it back in the days when you twisted a knob and then had to fine-tune the receiver). I felt like it was almost my personal secret then, something like Jean Shepherd's Ralphie feels before he decodes Annie's message. Except, this doesn't turn out to be a disappointment. The stories were intelligent, accessible, and timeless. This is TV doing what it should, before everything was about teen angst. (You know, I was a teen once and I don't remember having any angst. Maybe that was partly because my TV entertained me without suggesting I had to be glum to be cool. Maybe not.)
I've never seen it since and I've often wondered why not. It seems like the kind of thing that modern mystery fans would love to have, even if that meant buying it on DVD.