So far as I am aware, Episode 4 ("At Night All Cats are Gray") was the only occasion during which Boris Karloff and Christopher Lee ever appeared together. For that reason alone this series is worth a look.
It is also a very cleaver detective series featuring the inimitable Boris Karloff as a brilliant and unconventional one-eyed Scotland Yard sleuth. That is not the sort of role with which Boris Karloff is generally associated. However, he was actually a highly accomplished actor who was quite capable of playing all sorts of parts. It was no fault of his that he ended up being type cast as a "monster. For example, prior to his memorable performance the 1931 production of "Frankenstein", Karloff frequently appeared in gangster roles.
Karloff plays the erudite, one-eyed Colonel March who single-handedly runs Scotland Yard's "Department of Queer Complaints". Being the 1950s, that title has nothing whatever to do with homosexuality. Instead, it simply means that March is assigned all of the unusual cases that nobody else can manage to solve.