A few years ago I acquired 20 episodes of the series from an online seller. I was mildly impressed at first. I though the series was well done. Karloff's character, Colonel March, was well defined, and the stories were generally pleasing. However, over the years I have come to really love this modest little series.
The many reviews I've read on the series usually fluff it off as a low budget British TV series. That is most unkind. The productions values are very standard for the time. The mystery elements are not the draw of the series. Rather, it is Karloff's wonderful performance, mixed with the quirky elements of the stories. Karloff's Colonel March is an intelligent, slightly egoistical maverick. He works for Scotland Yard in the aptly named Department of Queer Complaints. Yet March is basically an acknowledged genius who works on his own and he has no supervisor. The toughest, most bizarre and whimsical cases are all thrown in March's lap.
My favourite episodes include; 1. The Abominable Snowman, where the snowy legend threatens members of March's own mountain climbing group. 2. Death and the Other Monkey, where March probes the murder of a scientist on the verge of a breakthrough. 3. The Sorcerer, March investigates the murder of a psychologist.
If you watch an episode and it doesn't impress you, try another. The series might grow on you, like it did with me.