Much to my delight, these two discs also include the 90-minute pilot episode of the series, 'Speedy Death', as well as the four, hour-long episdoes: 'Death at the Opera', 'The Rising of the Moon', 'Laurels are Poison' & 'The Worsted Viper'.
Diana Rigg is utterly superb as the intuitive psychoanalyst, Adela Bradley, bringing a devil-may-care attitude to matters of life and death. (Her asides to camera are sublime.)
If you can imagine the grandmother of Mrs Peel from the Avengers, Mrs Bradley is it!

Why Greg Dyke - the then director of the BBC - didn't commission more episodes of this fabulous series is an utter and complete mystery to me - maybe Adela Bradley could investigate?